Photog29 Query

Hello! I am a self-employed photographer. Some time ago I became aware that my photos were being used without authorisation by several companies. I started working with a copyright protection company in Germany that contacts the infringers and negotiates compensation for their use of my photos. The German company keeps 40% of these compensations and transfers the rest to me. I used to live abroad until recently and according to the local taxation, I didn't have to pay tax on these compensatory payments. Now, I am back in the UK and about to file my tax return. How do I indicate the nature of these compensations, please? As pure taxable income or as something else? Thank you in advance!