Income from previous employer

Hello, I have a question which is a bit complicated and I cannot find answers online. I resigned from my previous job in Hong Kong before I move to the UK. However, there are commissions that I made from transactions can only be paid after completion, which is after I moved and became a UK resident. My previous employer paid the commissions once the transactions are completed when I was already in the UK. Does these commissions taxable? As I worked for the company and made those transactions before becoming a UK resident, it’s only a delayed payout from previous employer. Thank you!

Hi,
Under the terms of the double taxation treaty, Income for work carried out on Hong Kong soil is only taxable there.
Thank you.