diff --git a/DLCS.Repository.Tests/Assets/ThumbReorganiserTests.cs b/DLCS.Repository.Tests/Assets/ThumbReorganiserTests.cs
index f9f3902a3..6fee8683e 100644
--- a/DLCS.Repository.Tests/Assets/ThumbReorganiserTests.cs
+++ b/DLCS.Repository.Tests/Assets/ThumbReorganiserTests.cs
@@ -204,6 +204,64 @@ public async Task EnsureNewLayout_CreatesExpectedResources_MixedAuthAndOpen()
                         "application/json"))
                 .MustHaveHappened();
         }
+        
+        [Fact]
+        public async Task EnsureNewLayout_CreatesExpectedResources_MixedAuthAndOpen_ImageSmallerThanThumbnail()
+        {
+            var rootKey = new ObjectInBucket {Bucket = "the-bucket", Key = "2/1/the-astronaut/"};
+            A.CallTo(() => bucketReader.GetMatchingKeys(rootKey))
+                .Returns(new[]
+                {
+                    "2/1/the-astronaut/full/200,/0/default.jpg",
+                    "2/1/the-astronaut/full/200,400/0/default.jpg",
+                    "2/1/the-astronaut/full/100,/0/default.jpg",
+                    "2/1/the-astronaut/full/100,200/0/default.jpg",
+                    "2/1/the-astronaut/full/50,/0/default.jpg",
+                    "2/1/the-astronaut/full/50,100/0/default.jpg"
+                });
+
+            A.CallTo(() => assetRepository.GetAsset(A<string>._))
+                .Returns(new Asset {Width = 300, Height = 600, ThumbnailPolicy = "TheBestOne", MaxUnauthorised = 350, Roles = "admin"});
+            A.CallTo(() => thumbPolicyRepository.GetThumbnailPolicy("TheBestOne"))
+                .Returns(new ThumbnailPolicy {Sizes = "1024,400,200,100"});
+            
+            // Act
+            var response = await sut.EnsureNewLayout(rootKey);
+
+            // Assert
+            response.Should().Be(ReorganiseResult.Reorganised);
+
+            // move jpg per thumbnail size
+            A.CallTo(() =>
+                    bucketReader.CopyWithinBucket("the-bucket",
+                        "2/1/the-astronaut/low.jpg",
+                        "2/1/the-astronaut/auth/600.jpg"))
+                .MustHaveHappened();
+            A.CallTo(() =>
+                    bucketReader.CopyWithinBucket("the-bucket", 
+                        "2/1/the-astronaut/full/200,400/0/default.jpg",
+                        "2/1/the-astronaut/auth/400.jpg"))
+                .MustHaveHappened();
+            A.CallTo(() =>
+                    bucketReader.CopyWithinBucket("the-bucket",
+                        "2/1/the-astronaut/full/100,200/0/default.jpg",
+                        "2/1/the-astronaut/open/200.jpg"))
+                .MustHaveHappened();
+            A.CallTo(() =>
+                    bucketReader.CopyWithinBucket("the-bucket", 
+                        "2/1/the-astronaut/full/50,100/0/default.jpg",
+                        "2/1/the-astronaut/open/100.jpg"))
+                .MustHaveHappened();
+            
+            // create sizes.json
+            const string expected = "{\"o\":[[100,200],[50,100]],\"a\":[[300,600],[200,400]]}";
+            A.CallTo(() =>
+                    bucketReader.WriteToBucket(
+                        A<ObjectInBucket>.That.Matches(o =>
+                            o.Bucket == "the-bucket" && o.Key == "2/1/the-astronaut/s.json"), expected,
+                        "application/json"))
+                .MustHaveHappened();
+        }
 
         [Fact]
         public async Task EnsureNewLayout_CreatesExpectedResources_HandlingRoundingDifference_Portrait()
diff --git a/DLCS.Repository/Assets/ThumbReorganiser.cs b/DLCS.Repository/Assets/ThumbReorganiser.cs
index c0ac4af3e..7f41b8c2c 100644
--- a/DLCS.Repository/Assets/ThumbReorganiser.cs
+++ b/DLCS.Repository/Assets/ThumbReorganiser.cs
@@ -90,7 +90,7 @@ public async Task<ReorganiseResult> EnsureNewLayout(ObjectInBucket rootKey)
             }
 
             // All the thumbnail jpgs will already exist and need copied up to root
-            await CreateThumbnails(rootKey, boundingSquares, thumbnailSizes, existingSizes);
+            await CreateThumbnails(rootKey, thumbnailSizes, existingSizes);
 
             // Create sizes json file last, as this dictates whether this process will be attempted again
             await CreateSizesJson(rootKey, thumbnailSizes);
@@ -125,32 +125,34 @@ private static List<Size> GetExistingSizesList(ThumbnailSizes thumbnailSizes, st
             return existingSizes;
         }
 
-        private async Task CreateThumbnails(ObjectInBucket rootKey, List<int> boundingSquares,
-            ThumbnailSizes thumbnailSizes, List<Size> existingSizes)
+        private async Task CreateThumbnails(ObjectInBucket rootKey, ThumbnailSizes thumbnailSizes,
+            List<Size> existingSizes)
         {
             var copyTasks = new List<Task>(thumbnailSizes.Count);
 
-            // low.jpg becomes the first in this list
-            var largestSize = boundingSquares[0];
+            var openSizes = thumbnailSizes.Open.Select(wh => Size.FromArray(wh)).ToList();
+            var authSizes = thumbnailSizes.Auth.Select(wh => Size.FromArray(wh)).ToList();
+            var largestSize = openSizes.Concat(authSizes).Max(sz => sz.MaxDimension);
+
+            // low.jpg becomes the largest sized thumb
             var largestSlug = thumbnailSizes.Auth.IsNullOrEmpty() ? thumbConsts.OpenSlug : thumbConsts.AuthorisedSlug;
             copyTasks.Add(bucketReader.CopyWithinBucket(rootKey.Bucket,
                 $"{rootKey.Key}low.jpg",
                 $"{rootKey.Key}{largestSlug}/{largestSize}.jpg"));
 
-            copyTasks.AddRange(ProcessThumbBatch(rootKey, thumbnailSizes.Auth, thumbConsts.AuthorisedSlug, largestSize,
+            copyTasks.AddRange(ProcessThumbBatch(rootKey, authSizes, thumbConsts.AuthorisedSlug, largestSize,
                 existingSizes));
-            copyTasks.AddRange(ProcessThumbBatch(rootKey, thumbnailSizes.Open, thumbConsts.OpenSlug, largestSize,
+            copyTasks.AddRange(ProcessThumbBatch(rootKey, openSizes, thumbConsts.OpenSlug, largestSize,
                 existingSizes));
 
             await Task.WhenAll(copyTasks);
         }
 
-        private IEnumerable<Task> ProcessThumbBatch(ObjectInBucket rootKey, IEnumerable<int[]> thumbnailSizes,
-            string slug, int largestSize, List<Size> existingSizes)
+        private IEnumerable<Task> ProcessThumbBatch(ObjectInBucket rootKey, IEnumerable<Size> thumbnailSizes,
+            string slug, int largestSize, IReadOnlyCollection<Size> existingSizes)
         {
-            foreach (var wh in thumbnailSizes)
+            foreach (var currentSize in thumbnailSizes)
             {
-                var currentSize = Size.FromArray(wh);
                 var maxDimension = currentSize.MaxDimension;
                 if (maxDimension == largestSize) continue;