One letter, written by students at Cwmnedd Primary School in Neath Port Talbot, described the colour bar as “horrendous, horrific and disgraceful”, saying it was “not right then, and it is not right now”.

Cuthbert was born to a Liverpool-born man of Jamaican heritage and Welsh mother, competing for Great Britain in the 1928 Amsterdam Olympics where he reached the quarter final.

He was the first black boxer to represent Great Britain, and the country’s third ever black Olympian, external.

In a 20-year professional career, he won 151 bouts, drew 22 and lost 69.

But he was denied the right to fight for the British title because, according to BBBoC’s rules, fighters had to have “two white parents”.

Having seen The Fight – which recently completed runs at Swansea’s Dylan Thomas Theatre and Theatr Brycheiniog in Brecon, Powys – students from a number of schools in south Wales were inspired to write the letters calling for an apology.

One letter from Katie H and Morgan G, students at Cwmnedd Primary School in Neath Port Talbot, said it was “unfair” that boxers without white, British parents were not allowed to fight for the British title.

“The colour bar was horrendous, horrific and disgraceful. It was not right then, and it is not right now. The awful act can be reconciled by apologising to the boxers,” the letter said.

“It was entirely the children’s idea to pen letters to the British Boxing Board of Control,” said Aisling Brady Saunders, deputy headteacher at St Joseph’s Junior School in Port Talbot, another school taking part.

“They feel very strongly that Cuthbert Taylor, his surviving family and all boxers affected by the colour bar rule should have an apology and be recognised for their sporting achievements.”

The BBBoc has said boxing was one of the “most diverse and inclusive sports” in the UK and acknowledged that the colour bar was wrong, but did not apologise.

The UK government’s Department for Digital, Culture, Media and Sport, external (DCMS) said an apology was firstly a matter for the BBBoC and that it “does not wish to unduly influence their response”, adding that it will respond to the letters “in due course”.

It added “by today’s standards, the prohibition that was in place in the early part of the last century was plainly racist”.