`Donald Trump has posthumously pardoned former boxing champion Jack Johnson, who was convicted in a racially charged case early in the 20th century.

“It’s my honour to do it”, Mr Trump said during an Oval Office signing ceremony. “It’s about time”.

The president had earlier said he was mulling a pardon after the actor Sylvester Stallone - who is known for portraying an underdog fighter in the film “Rocky” - called to share “the story of heavyweight boxing champion Jack Johnson”.

“His trials and tribulations were great, his life complex and controversial. Others have looked at this over the years, most thought it would be done, but yes, I am considering a Full Pardon!” Mr Trump wrote in an April tweet.

Standing with a number of boxers behind Mr Trump as the president signed Mr Jackson’s pardon, Mr Stallone said the move “has been a long time coming”.

As the first black man to win the heavyweight boxing championship, Mr Johnson became an icon for African-Americans struggling under racial prejudice.

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But his relationships with white women - three of whom he married - led Mr Johnson to be charged under a law called the Mann Act that was intended to combat human trafficking.

After the mother of Mr Johnson’s second wife, Lucille Cameron, alleged that Mr Johnson had abducted Ms Cameron, he faced federal charges.

Kate Geraghty winning a kickboxing match in Thailand

That case ultimately collapsed when Ms Cameron refused to cooperate, but an all-white jury convicted him on a subsequent case brought in relation to the boxer’s former relationship with a white woman named Belle Schreiber.