Early in Henry VIII’s reign the Venetian Ambassador described him as “the handsomest potentate I ever set eyes on, with an extremely fine calf to his leg . . . and a round face so very beautiful that it would become a pretty woman”.

Six wives, one Reformation and a lot of feasting later, Henry had become, by the time of his death in 1547, larger than life.

Just how large, and when, has long been a source of speculation, but research by the Royal Armouries in Leeds has now provided the nearest thing to a definitive set of vital statistics. The findings will go on show at the Tower of London from April.

Analysis of suits of armour made for Henry and reunited for the first time since the Tudor era proves that the king was 6ft 1in — well above average even today. As a young man he had a sportsman’s physique, with a waist measuring about 32in and a 39in chest. By his late forties, his waist had drifted to nearer 48in and in his final years he appears to have been carrying a 52in waist and 53in chest.

Mark McCarthy, Professor of Diabetes at the University of Oxford, said that that made Henry “way over the threshold for obesity” — although it did not necessarily make him unhealthily fat. Some Olympic athletes have similar proportions, much of it muscle.

Peter Armstrong, the director of the Royal Armouries, put it more bluntly. “He was an absolute monster,” he said.

This is Henry VIII’s year. The 500th anniversary of his coronation will be commemorated by several exhibitions. The British Library and the Royal Collection at Windsor Castle are displaying spectacular portraits. Hampton Court has a continuing show about the young Henry and special events lined up including Rick Wakeman performing his 1972 album The Six Wives of Henry VIII live for the first time.

The Royal Armouries show, Henry VIII: Dressed to Kill, will be built around five complete suits of armour from the Tower, the Armouries in Leeds and the Metropolitan Museum in New York, as well as incomplete ones. “It will be the one place where you see the king in three dimensions and get an idea of his immense physical presence,” Graeme Rimer, academic director of the Royal Armouries, said. “The armour tells us unequivocally that he was 6ft 1in and that he was pretty enormous but still vigorous at the end of his life.”

Court painters were prone to flattery, and, in any case, the fashion was for loose hanging garments that obscured the wearer’s dimensions.

A full suit of armour gives a much better indication of the wearer’s actual size – even though Henry spent fortunes on hiring the finest European armourers, men with a Savile Row tailor’s knack of disguising a paunch.

Henry was never the “fat, boorish king throwing chicken bones over his shoulder” that Charles Laughton embodied on film. He is as likely to have grown fat because of a medical condition as overeating, Mr Rimer said.

The popular idea of the ageing Henry having to be hoisted on to his horse with a crane is also “nonsense”. “There is no evidence that he was incapacitated in any way by his weight; the armour suggests that he was still riding and still active late in life.”