Millionaire apologises for snatching Majchrzak’s souvenir cap from young fan at US Open

• Polish businessman Piotr Szczerek says: I made a grave mistake'

• Majchrzak had given cap to boy in crowd after five-set victory

Moments after the tennis player Kamil Majchrzak celebrated the biggest win of his career at the US Open last week, he handed his cap to a beaming young boy. What happened next sparked tears, outrage, a detective hunt across social media and, finally, a grovelling apology.

It came from Piotr Szczerek, a millionaire businessman from Poland, who had snatched the cap out of the boy's hand and stuffed it into his bag. Videos of the incident showed the youngster looking deeply upset and asking: What are you doing?" while Majchrzak - who was oblivious to the situation after his five-set victory against the ninth seed, Karen Khachanov - walked away.