diff --git a/app/controllers/duplicate_logs_controller.rb b/app/controllers/duplicate_logs_controller.rb
index 43b8524bf..17b526bef 100644
--- a/app/controllers/duplicate_logs_controller.rb
+++ b/app/controllers/duplicate_logs_controller.rb
@@ -1,10 +1,15 @@
 class DuplicateLogsController < ApplicationController
+  before_action :authenticate_user!
   before_action :find_resource_by_named_id
 
   def show
-    @duplicate_logs = @log.class.duplicate_logs_for_organisation(current_user.organisation_id, @log)
-    @all_duplicates = [@log, *@duplicate_logs]
-    @duplicate_check_questions = duplicate_check_question_ids.map { |question_id| @log.form.get_question(question_id, @log) }.compact
+    if @log
+      @duplicate_logs = @log.class.duplicate_logs_for_organisation(current_user.organisation_id, @log)
+      @all_duplicates = [@log, *@duplicate_logs]
+      @duplicate_check_questions = duplicate_check_question_ids.map { |question_id| @log.form.get_question(question_id, @log) }.compact
+    else
+      render_not_found
+    end
   end
 
 private
diff --git a/spec/requests/duplicate_logs_controller_spec.rb b/spec/requests/duplicate_logs_controller_spec.rb
index 69e66ad03..502de78dd 100644
--- a/spec/requests/duplicate_logs_controller_spec.rb
+++ b/spec/requests/duplicate_logs_controller_spec.rb
@@ -20,70 +20,93 @@ RSpec.describe DuplicateLogsController, type: :request do
       )
     end
 
-    before do
-      allow(user).to receive(:need_two_factor_authentication?).and_return(false)
-      sign_in user
-    end
-
     describe "GET" do
-      context "with multiple duplicate lettings logs" do
-        let(:duplicate_logs) { create_list(:lettings_log, 2, :completed) }
-
-        before do
-          allow(LettingsLog).to receive(:duplicate_logs_for_organisation).and_return(duplicate_logs)
+      context "when user is not signed in" do
+        it "redirects to sign in page" do
           get "/lettings-logs/#{lettings_log.id}/duplicate-logs"
+          expect(response).to redirect_to("/account/sign-in")
         end
+      end
 
-        it "displays links to all the duplicate logs" do
-          expect(page).to have_link("Log #{lettings_log.id}", href: "/lettings-logs/#{lettings_log.id}")
-          expect(page).to have_link("Log #{duplicate_logs.first.id}", href: "/lettings-logs/#{duplicate_logs.first.id}")
-          expect(page).to have_link("Log #{duplicate_logs.second.id}", href: "/lettings-logs/#{duplicate_logs.second.id}")
-        end
+      context "when the user is from different organisation" do
+        let(:other_user) { create(:user) }
 
-        it "displays check your answers for each log with correct questions" do
-          expect(page).to have_content("Q1 - Stock owner", count: 3)
-          expect(page).to have_content("Q5 - Tenancy start date", count: 3)
-          expect(page).to have_content("Q7 - Tenant code", count: 3)
-          expect(page).to have_content("Q12 - Postcode", count: 3)
-          expect(page).to have_content("Q32 - Lead tenant’s age", count: 3)
-          expect(page).to have_content("Q33 - Lead tenant’s gender identity", count: 3)
-          expect(page).to have_content("Q37 - Lead tenant’s working situation", count: 3)
-          expect(page).to have_content("Household rent and charges", count: 3)
-          expect(page).to have_link("Change", count: 24)
+        before do
+          allow(other_user).to receive(:need_two_factor_authentication?).and_return(false)
+          sign_in other_user
         end
 
-        it "displays buttons to delete" do
-          expect(page).to have_link("Keep this log and delete duplicates", count: 3)
+        it "renders page not found" do
+          get "/lettings-logs/#{lettings_log.id}/duplicate-logs"
+          expect(response).to have_http_status(:not_found)
         end
       end
 
-      context "with multiple duplicate sales logs" do
-        let(:duplicate_logs) { create_list(:sales_log, 2, :completed) }
-
+      context "when user is signed in" do
         before do
-          allow(SalesLog).to receive(:duplicate_logs_for_organisation).and_return(duplicate_logs)
-          get "/sales-logs/#{sales_log.id}/duplicate-logs"
+          allow(user).to receive(:need_two_factor_authentication?).and_return(false)
+          sign_in user
         end
 
-        it "displays links to all the duplicate logs" do
-          expect(page).to have_link("Log #{sales_log.id}", href: "/sales-logs/#{sales_log.id}")
-          expect(page).to have_link("Log #{duplicate_logs.first.id}", href: "/sales-logs/#{duplicate_logs.first.id}")
-          expect(page).to have_link("Log #{duplicate_logs.second.id}", href: "/sales-logs/#{duplicate_logs.second.id}")
-        end
+        context "with multiple duplicate lettings logs" do
+          let(:duplicate_logs) { create_list(:lettings_log, 2, :completed) }
+
+          before do
+            allow(LettingsLog).to receive(:duplicate_logs_for_organisation).and_return(duplicate_logs)
+            get "/lettings-logs/#{lettings_log.id}/duplicate-logs"
+          end
+
+          it "displays links to all the duplicate logs" do
+            expect(page).to have_link("Log #{lettings_log.id}", href: "/lettings-logs/#{lettings_log.id}")
+            expect(page).to have_link("Log #{duplicate_logs.first.id}", href: "/lettings-logs/#{duplicate_logs.first.id}")
+            expect(page).to have_link("Log #{duplicate_logs.second.id}", href: "/lettings-logs/#{duplicate_logs.second.id}")
+          end
+
+          it "displays check your answers for each log with correct questions" do
+            expect(page).to have_content("Q1 - Stock owner", count: 3)
+            expect(page).to have_content("Q5 - Tenancy start date", count: 3)
+            expect(page).to have_content("Q7 - Tenant code", count: 3)
+            expect(page).to have_content("Q12 - Postcode", count: 3)
+            expect(page).to have_content("Q32 - Lead tenant’s age", count: 3)
+            expect(page).to have_content("Q33 - Lead tenant’s gender identity", count: 3)
+            expect(page).to have_content("Q37 - Lead tenant’s working situation", count: 3)
+            expect(page).to have_content("Household rent and charges", count: 3)
+            expect(page).to have_link("Change", count: 24)
+          end
 
-        it "displays check your answers for each log with correct questions" do
-          expect(page).to have_content("Owning organisation", count: 3)
-          expect(page).to have_content("Q1 - Sale completion date", count: 3)
-          expect(page).to have_content("Q2 - Purchaser code", count: 3)
-          expect(page).to have_content("Q20 - Lead buyer’s age", count: 3)
-          expect(page).to have_content("Q21 - Buyer 1’s gender identity", count: 3)
-          expect(page).to have_content("Q25 - Buyer 1's working situation", count: 3)
-          expect(page).to have_content("Q15 - Postcode", count: 3)
-          expect(page).to have_link("Change", count: 21)
+          it "displays buttons to delete" do
+            expect(page).to have_link("Keep this log and delete duplicates", count: 3)
+          end
         end
 
-        it "displays buttons to delete" do
-          expect(page).to have_link("Keep this log and delete duplicates", count: 3)
+        context "with multiple duplicate sales logs" do
+          let(:duplicate_logs) { create_list(:sales_log, 2, :completed) }
+
+          before do
+            allow(SalesLog).to receive(:duplicate_logs_for_organisation).and_return(duplicate_logs)
+            get "/sales-logs/#{sales_log.id}/duplicate-logs"
+          end
+
+          it "displays links to all the duplicate logs" do
+            expect(page).to have_link("Log #{sales_log.id}", href: "/sales-logs/#{sales_log.id}")
+            expect(page).to have_link("Log #{duplicate_logs.first.id}", href: "/sales-logs/#{duplicate_logs.first.id}")
+            expect(page).to have_link("Log #{duplicate_logs.second.id}", href: "/sales-logs/#{duplicate_logs.second.id}")
+          end
+
+          it "displays check your answers for each log with correct questions" do
+            expect(page).to have_content("Owning organisation", count: 3)
+            expect(page).to have_content("Q1 - Sale completion date", count: 3)
+            expect(page).to have_content("Q2 - Purchaser code", count: 3)
+            expect(page).to have_content("Q20 - Lead buyer’s age", count: 3)
+            expect(page).to have_content("Q21 - Buyer 1’s gender identity", count: 3)
+            expect(page).to have_content("Q25 - Buyer 1's working situation", count: 3)
+            expect(page).to have_content("Q15 - Postcode", count: 3)
+            expect(page).to have_link("Change", count: 21)
+          end
+
+          it "displays buttons to delete" do
+            expect(page).to have_link("Keep this log and delete duplicates", count: 3)
+          end
         end
       end
     end