diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 62ccb2d3b8..9231b35e33 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config --auto-gen-only-exclude --exclude-limit 1000`
-# on 2024-04-24 16:19:07 UTC using RuboCop version 1.63.3.
+# on 2024-05-21 08:38:48 UTC using RuboCop version 1.63.5.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -244,10 +244,11 @@ Metrics/AbcSize:
     - 'spec/support/seed_helpers.rb'
     - 'spec/support/validation_helpers.rb'
 
-# Offense count: 19
+# Offense count: 20
 # Configuration parameters: CountComments, Max, CountAsOne.
 Metrics/ClassLength:
   Exclude:
+    - 'app/controllers/case_workers/claims_controller.rb'
     - 'app/controllers/external_users/claims_controller.rb'
     - 'app/interfaces/api/entities/search_result.rb'
     - 'app/interfaces/api/v1/dropdown_data.rb'
diff --git a/Gemfile b/Gemfile
index 778453978e..517b82bd42 100644
--- a/Gemfile
+++ b/Gemfile
@@ -61,6 +61,7 @@ gem 'active_storage_validations'
 gem 'faraday', '~> 2.10'
 gem 'faraday-follow_redirects', '~> 0.3'
 gem 'puma'
+gem 'oauth2'
 
 group :development, :test do
   gem 'annotate'
diff --git a/Gemfile.lock b/Gemfile.lock
index 55701b5854..ac93069d1f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -381,6 +381,8 @@ GEM
     msgpack (1.7.2)
     multi_json (1.15.0)
     multi_test (1.1.0)
+    multi_xml (0.7.1)
+      bigdecimal (~> 3.1)
     multipart-post (2.4.1)
     mustermann (3.0.0)
       ruby2_keywords (~> 0.0.1)
@@ -407,6 +409,13 @@ GEM
       racc (~> 1.4)
     notifications-ruby-client (6.2.0)
       jwt (>= 1.5, < 3)
+    oauth2 (2.0.9)
+      faraday (>= 0.17.3, < 3.0)
+      jwt (>= 1.0, < 3.0)
+      multi_xml (~> 0.5)
+      rack (>= 1.2, < 4)
+      snaky_hash (~> 2.0)
+      version_gem (~> 1.1)
     orm_adapter (0.5.0)
     paper_trail (15.1.0)
       activerecord (>= 6.1)
@@ -597,6 +606,9 @@ GEM
       capybara (~> 3.32)
       site_prism-all_there (> 2, < 5)
     site_prism-all_there (3.0.5)
+    snaky_hash (2.0.1)
+      hashie
+      version_gem (~> 1.1, >= 1.1.1)
     sprockets (4.2.1)
       concurrent-ruby (~> 1.0)
       rack (>= 2.2.4, < 4)
@@ -637,6 +649,7 @@ GEM
       activesupport
     vcr (6.3.0)
       base64
+    version_gem (1.1.4)
     virtus (2.0.0)
       axiom-types (~> 0.1)
       coercible (~> 1.0)
@@ -725,6 +738,7 @@ DEPENDENCIES
   net-smtp
   net-ssh (~> 7.2)
   nokogiri (~> 1.16)
+  oauth2
   paper_trail (~> 15.1.0)
   parallel_tests
   pg (~> 1.5.7)
diff --git a/app/controllers/case_workers/claims_controller.rb b/app/controllers/case_workers/claims_controller.rb
index 6061416712..92813f3808 100644
--- a/app/controllers/case_workers/claims_controller.rb
+++ b/app/controllers/case_workers/claims_controller.rb
@@ -16,6 +16,7 @@ class ClaimsController < CaseWorkers::ApplicationController
     before_action :filter_archived_claims,  only: [:archived]
     before_action :sort_claims,             only: %i[index archived]
     before_action :set_claim, only: %i[show messages download_zip]
+    before_action :set_show_maat_details
 
     include ReadMessages
     include MessageControlsDisplay
@@ -131,5 +132,14 @@ def sort_claims
     def criteria_params
       { sorting: sort_column, direction: sort_direction, page: current_page, limit: page_size, search: search_terms }
     end
+
+    def set_show_maat_details
+      if params[:maat_details].present?
+        @show_maat_details = params[:maat_details] == 'on'
+        current_user.save_setting!(maat_details: @show_maat_details)
+      else
+        @show_maat_details = current_user.setting?(:maat_details) || false
+      end
+    end
   end
 end
diff --git a/app/services/maat_service.rb b/app/services/maat_service.rb
index 8ac57929a5..bd3db05341 100644
--- a/app/services/maat_service.rb
+++ b/app/services/maat_service.rb
@@ -11,7 +11,8 @@ def call
 
     {
       case_number: data['caseId'],
-      representation_order_date: data['crownRepOrderDate']
+      representation_order_date: data['crownRepOrderDate'],
+      asn: data['arrestSummonsNo']
     }
   end
 end
diff --git a/app/services/maat_service/connection.rb b/app/services/maat_service/connection.rb
index be84ccd3b3..d96335a249 100644
--- a/app/services/maat_service/connection.rb
+++ b/app/services/maat_service/connection.rb
@@ -3,35 +3,22 @@ class Connection
     include Singleton
 
     def fetch(maat_reference)
-      JSON.parse(client.get("assessment/rep-orders/#{maat_reference}").body)
-    rescue Faraday::ConnectionFailed
+      JSON.parse(access.get("assessment/rep-orders/#{maat_reference}").body)
+    rescue OAuth2::Error
       {}
     end
 
     private
 
-    def client
-      @client ||= Faraday.new(Settings.maat_api_url, request: { timeout: 2 }) do |conn|
-        conn.headers['Authorization'] = "Bearer #{oauth_token}"
-      end
-    end
-
-    def oauth_token
-      response = Faraday.post(Settings.maat_api_oauth_url, request_params, request_headers)
-      JSON.parse(response.body)['access_token']
-    end
+    def access = @access ||= client.client_credentials.get_token
 
-    def request_params
-      {
-        client_id: Settings.maat_api_oauth_client_id,
-        client_secret: Settings.maat_api_oauth_client_secret,
-        scope: Settings.maat_api_oauth_scope,
-        grant_type: 'client_credentials'
-      }
-    end
-
-    def request_headers
-      { content_type: 'application/x-www-form-urlencoded' }
+    def client
+      @client ||= OAuth2::Client.new(
+        Settings.maat_api_oauth_client_id,
+        Settings.maat_api_oauth_client_secret,
+        site: Settings.maat_api_url,
+        token_url: Settings.maat_api_oauth_url
+      )
     end
   end
 end
diff --git a/app/views/shared/_claim.html.haml b/app/views/shared/_claim.html.haml
index bbca000b72..d07e073df9 100644
--- a/app/views/shared/_claim.html.haml
+++ b/app/views/shared/_claim.html.haml
@@ -84,7 +84,12 @@
       %h3.govuk-heading-m
         = t('.defendants')
 
-    = render partial: 'shared/claim_defendants', locals: {defendants: claim.defendants }
+    - if @show_maat_details
+      = govuk_link_to t('.disable_maat_details'), '?maat_details=off'
+      = render partial: 'shared/claim_defendants_with_maat', locals: {defendants: claim.defendants }
+    - else
+      = govuk_link_to t('.enable_maat_details'), '?maat_details=on'
+      = render partial: 'shared/claim_defendants', locals: {defendants: claim.defendants }
 
 - else
   .govuk-grid-row
diff --git a/app/views/shared/_claim_defendant_details_with_maat.html.haml b/app/views/shared/_claim_defendant_details_with_maat.html.haml
new file mode 100644
index 0000000000..8b0fcf95f4
--- /dev/null
+++ b/app/views/shared/_claim_defendant_details_with_maat.html.haml
@@ -0,0 +1,37 @@
+.app-card--defendant
+  %h4.govuk-heading-s
+    = t('.defendant', context: index)
+
+  = govuk_summary_list do
+    = govuk_summary_list_row_collection( t('external_users.claims.defendants.defendant_fields.full_name') ) { defendant.name }
+
+    - if defendant.date_of_birth.present?
+      = govuk_summary_list_row_collection( t('external_users.claims.defendants.defendant_fields.date_of_birth') ) { defendant.date_of_birth.strftime(Settings.date_format) rescue '' }
+
+    - unless @claim.lgfs? && @claim.interim?
+      = govuk_summary_list_row_collection( t('external_users.claims.defendants.defendant_fields.judical_apportionment') ) { defendant.order_for_judicial_apportionment == true ? t('global_yes') : t('global_no') }
+
+
+  - if defendant.representation_orders.any?
+    = govuk_table do
+      = govuk_table_caption do
+        = t('shared.claim.reporders')
+
+      = govuk_table_thead_collection [t('.date'),
+      t('external_users.claims.defendants.representation_order_fields.maat_reference_number'),
+      t('.asn')]
+
+      = govuk_table_tbody do
+        - defendant.representation_orders.each do | representation_order |
+          = govuk_table_row do
+            = govuk_table_td('data-label': t('.date')) do
+              = representation_order.representation_order_date.strftime(Settings.date_format) rescue ''
+
+            = govuk_table_td('data-label': t('external_users.claims.defendants.representation_order_fields.maat_reference_number')) do
+              = representation_order.maat_reference
+
+            = govuk_table_td('data-label': t('.asn')) do
+              = representation_order.maat_details[:asn]
+
+  - else
+    = govuk_inset_text(t('.no_reporder'))
diff --git a/app/views/shared/_claim_defendants.html.haml b/app/views/shared/_claim_defendants.html.haml
index 7d89a46759..699acc6d4d 100644
--- a/app/views/shared/_claim_defendants.html.haml
+++ b/app/views/shared/_claim_defendants.html.haml
@@ -1,3 +1,3 @@
 - defendants.each_with_index do | defendant, index |
   .govuk-grid-column-one-half
-    = render partial: 'shared/claim_defendant_details', locals: { defendant: present(defendant, CaseWorkers::DefendantPresenter), index: index += 1 }
+    = render partial: 'shared/claim_defendant_details', locals: { defendant:, index: index += 1 }
diff --git a/app/views/shared/_claim_defendants_with_maat.html.haml b/app/views/shared/_claim_defendants_with_maat.html.haml
new file mode 100644
index 0000000000..836880bfb4
--- /dev/null
+++ b/app/views/shared/_claim_defendants_with_maat.html.haml
@@ -0,0 +1,3 @@
+- defendants.each_with_index do | defendant, index |
+  .govuk-grid-column-one-half
+    = render partial: 'shared/claim_defendant_details_with_maat', locals: { defendant: present(defendant, CaseWorkers::DefendantPresenter), index: index += 1 }
diff --git a/config/locales/en.yml b/config/locales/en.yml
index dc9786dd45..fbecafae6e 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -2026,11 +2026,20 @@ en:
       banner_paragraph: This is to enable routine maintenance work to be carried out. Please save and close any work before this time.
     claim_defendants:
       defendants: Defendants
+      enable_maat_details: Enable MAAT details (experimental)
+      disable_maat_details: Disable MAAT details (experimental)
     claim_defendant_details:
       caption: 'Defendant: Additional information'
       date: Order date
       defendant: Defendant %{context}
       no_reporder: No representation orders have been supplied for this defendant.
+    claim_defendant_details_with_maat:
+      caption: 'Defendant: Additional information'
+      date: Order date
+      defendant: Defendant %{context}
+      no_reporder: No representation orders have been supplied for this defendant.
+      case_number_from_maat: Case number from MAAT (experimental)
+      asn: ASN (experimental)
     evidence_checklist:
       caption: 'Supporting evidence checklist'
       summary: 'Note: To best navigate this table, step down the second column'
@@ -2100,6 +2109,8 @@ en:
       submit_date: Claim submitted
       trial_concluded: Trial concluded
       prosecution_evidence: Prosecution evidence
+      enable_maat_details: Enable MAAT details (experimental)
+      disable_maat_details: Disable MAAT details (experimental)
     claims:
       interim_claim_info:
         fields: *interim_claim_info_fields
diff --git a/config/settings.yml b/config/settings.yml
index 1144f96cc6..0ca38be721 100644
--- a/config/settings.yml
+++ b/config/settings.yml
@@ -234,7 +234,6 @@ maat_regexp: !ruby/regexp <%= ENV['MAAT_REGEXP'] || '/^[2-9][0-9]{6}$/' %>
 maat_api_url: <%= ENV['MAAT_API_URL'] %>
 maat_api_oauth_client_id: <%= ENV['OAUTH_CLIENT_ID'] %>
 maat_api_oauth_client_secret: <%= ENV['OAUTH_CLIENT_SECRET'] %>
-maat_api_oauth_scope: <%=ENV['OAUTH_SCOPE'] %>
 maat_api_oauth_url: <%=ENV['OAUTH_URL']%>
 
 secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>
diff --git a/spec/services/maat_service_spec.rb b/spec/services/maat_service_spec.rb
index 6b89974ffa..3d8e0c999f 100644
--- a/spec/services/maat_service_spec.rb
+++ b/spec/services/maat_service_spec.rb
@@ -1,8 +1,21 @@
 RSpec.describe MaatService do
   before do
-    allow(Settings).to receive_messages(maat_api_url: 'https://example.com', maat_api_oauth_url: 'https://example.com/oauth')
-    stub_request(:post, 'https://example.com/oauth')
-      .to_return(body: { access_token: 'test_token' }.to_json)
+    allow(OAuth2::Client).to receive(:new).and_return(
+      OAuth2::Client.new(
+        Settings.maat_api_oauth_client_id,
+        Settings.maat_api_oauth_client_secret,
+        site: 'https://example.com',
+        token_url: 'https://example.com/oauth'
+      )
+    )
+    stub_request(:post, 'https://example.com/oauth').to_return(
+      body: {
+        access_token: 'test-token',
+        expires_in: 3600,
+        token_type: 'Bearer'
+      }.to_json,
+      headers: { 'content-type': 'application/json' }
+    )
   end
 
   describe '.call' do
@@ -14,10 +27,16 @@
     context 'with a valid MAAT reference' do
       before do
         stub_request(:get, "https://example.com/assessment/rep-orders/#{maat_reference}")
-          .to_return(body: { caseId: 'TEST12345678', crownRepOrderDate: '2024-03-28' }.to_json)
+          .to_return(
+            body: {
+              caseId: 'TEST12345678',
+              crownRepOrderDate: '2024-03-28',
+              arrestSummonsNo: 'ABCDEF'
+            }.to_json
+          )
       end
 
-      it { is_expected.to eq({ case_number: 'TEST12345678', representation_order_date: '2024-03-28' }) }
+      it { is_expected.to eq({ case_number: 'TEST12345678', representation_order_date: '2024-03-28', asn: 'ABCDEF' }) }
     end
 
     context 'with a valid MAAT reference with no date' do
@@ -26,7 +45,7 @@
           .to_return(body: { caseId: 'TEST12345678' }.to_json)
       end
 
-      it { is_expected.to eq({ case_number: 'TEST12345678', representation_order_date: nil }) }
+      it { is_expected.to eq({ case_number: 'TEST12345678', representation_order_date: nil, asn: nil }) }
     end
 
     context 'with an unknown MAAT reference' do
@@ -35,7 +54,7 @@
           .to_return(status: 404, body: { message: "No Rep Order found for ID: #{maat_reference}" }.to_json)
       end
 
-      it { is_expected.to eq({ case_number: nil, representation_order_date: nil }) }
+      it { is_expected.to eq({ case_number: nil, representation_order_date: nil, asn: nil }) }
     end
 
     context 'when unauthorized' do
@@ -44,18 +63,20 @@
           .to_return(status: 401, body: { message: 'Unauthorized' }.to_json)
       end
 
-      it { is_expected.to eq({ case_number: nil, representation_order_date: nil }) }
+      it { is_expected.to eq({ case_number: nil, representation_order_date: nil, asn: nil }) }
     end
 
     context 'when the OAuth settings are not correct' do
       before do
         stub_request(:post, 'https://example.com/oauth')
-          .to_return(status: 400, body: { error: 'invalid_client' }.to_json)
-        stub_request(:get, "https://example.com/assessment/rep-orders/#{maat_reference}")
-          .to_return(status: 401, body: { message: 'Unauthorized' }.to_json)
+          .to_return(
+            status: 400,
+            body: { error: 'invalid_client' }.to_json,
+            headers: { 'content-type': 'application/json' }
+          )
       end
 
-      it { is_expected.to eq({ case_number: nil, representation_order_date: nil }) }
+      it { is_expected.to eq({ case_number: nil, representation_order_date: nil, asn: nil }) }
     end
   end
 end