Prince Harry is said to have hurt his ankle eight hours earlier after leaping from the Goring Hotel veranda.
As he stood at his brother’s side in Westminster Abbey waiting for the bride to arrive, Prince Harry drew more than a few questioning glances.
Despite his smart military uniform, the young Royal appeared a little jaded, with his hair askew and a definite look of someone who had not had enough sleep.
Now a possible answer to the question of why Harry seemed a touch under par on Royal Wedding day has emerged.
Sources have revealed that the best man was out socialising until 3am -- eight hours before the wedding.
And he is said to have left the party venue with an athletic leap from a balcony which saw him land awkwardly on one ankle.
The scene of the raucous goings-on was The Goring, the hotel which the Middleton family had taken over in the days before the wedding on Friday, April 29.
On the Thursday evening, a group of the young Royal circle had congregated in a bar there and were enjoying themselves heartily.
The festivities came to an end only at 3am when a young copper-haired reveller casually jumped off a veranda balcony, landing with a clumsy thump on a lawn 6ft below -- to roars of laughter from his friends.
According to sources, that reveller was the athletic Harry, whose looming day of duty had not stopped him sharing a few drinks with friends. An onlooker said: ‘Harry was with Pippa Middleton and Chelsy Davy among other friends for some pre-wedding drinks’.
‘He was the life and soul of the party until the early hours’.
Harry then made his way back to Clarence House, just a stone’s throw away, to get some shut-eye in the little time he had left until sunrise.
Palace aides said Harry had dined that evening with his brother, Prince Charles and Camilla at Clarence House, but would not be drawn on what Harry got up to when they retired to bed.
A spokesman said: ‘Prince Harry had a private dinner with his brother, Prince Charles and the Duchess of Cornwall. What he did after that is a private matter.’