Travel And Covid paperwork

I am responsible for a school boy who is returning home to his parents in China in June. He is travelling on a UK passport from London to Copenhagen, in transit at Copenhagen (for 8 hours) before catching a connecting flight to Shanghai.
We are making arrangements for Chinese Embassy-approved covid tests in the UK and will register and apply for a digital health declaration form. My question - does the boy (who is 16) have to repeat both tests at Copenhagen airport during transit and resubmit results to Chinese embassy in Denmark? His UK test will be within 48 hours of travel from Denmark. Thank you for your advice.