Thanks Peter.
I gave it a go, but I don't think I was successful. It boosted a 15Mb RAW file into a 72MB DNG file. The strange thing is the pixel dimensions collapsed from 5000 x 3000 to 1024 x 768.
I opened the DNG file in Photoshop and saved it as a jpeg. This time it was 12Mb (not as big as the original).
I also opened the DNG in Lightroom and this was exported at its largest resolution - a 12Mb jpeg.
Finally I cropped the image to 1400 x 1000 (1.4Mb) to give the following:

I think I am missing a trick here.