Prince William's drinking has earned him the nickname "five martinis Willy"

Mike, who is married to William's cousin Zara, 42, told Metro: "To be fair to him the one pint Willy name was several years out of date and we have given him a bit of training. He can now manage more than one pint.

"We call him five martinis Willy now. I think he's keen for it to be out there that he can manage more than a pint."

Mike first revealed he had called William "one pint Willy" in December when questioned on rugby league hero Rob Burrow's podcast.

He said at the time William is "not the best" at drinking, adding about royal nicknames: "For the Prince of Wales, he is known as 'One-Pint Willy'. He is known to me as 'One-Pint Willy' because he's not the best of drinkers.

"Coming from (rugby) where it's built on the social aspect and a couple of beers being sunk quite often.

"So, that is one that I will definitely give away for the Prince of Wales, One-Pint Willy, there you go."

Mike then apologised for putting the royal's family nickname in public.

Zara, who appeared on the podcast alongside her husband, looked embarrassed by his confession as she replied: "Oh my God, you're in so much trouble."

Mike, who is a close friend of William's, laughed it off and said: "Sorry, sorry sir!"

He also shared the pet name he and his wife call one another, admitting:

"We basically call each other 'Munchkins' a lot, don't we? Or 'My Love'.

"I normally use Munchkin, don't know why that started but it has stuck and it stays!"

Zara admitted that she has another two-word nickname that her husband is saved as on her phone which ends in "kitten", but stayed tight-lipped on the whole name.