The Queen and Duke of Edinburgh will have gone to bed. Mingling with other VIP guests, among them crowned heads of state, will be over.
As will that nerve-wracking first kiss expected by the crowds.
Only then will the bride and groom really relax.
Following the evening do hosted by Prince Charles for 300 close family and friends, Prince William and his new Princess will turn some of the opulent state rooms in Buckingham Palace into a nightclub.
The idea is one tried by William and Harry before. As teenagers, the two Princes used to party at Club H, a bar in their father’s Highgrove estate in Gloucestershire, where they could let their hair down from prying eyes.
Of course, this time the set up will be slightly more fancy.
According to the Daily Mail, professional DJ, decks, lights and a cocktail bar are being organised.
“William and Kate have said they want a proper knees-up,” a source told the paper. “They have been working on a playlist – they both love music and want some cheesy songs during the night.”
Among those strutting their stuff could be filmmaker Guy Ritchie, a distant cousin of Kate’s, who apparently has an invitation to the big occasion.
He may not stay too long as his pregnant girlfriend Jacqui Ainsley has not been invited.
Palace staff may also see Rowan Atkinson boogying on the dancefloor. The comedian is a close friend of the Prince of Wales.
It’s also known the groom has invited four of his former loves, who are now friends of his and Kate’s.
Among them is Jecca Craig, the daughter of a wealthy African conservationist, who hosted the royal pair, during the holiday on which the Prince proposed.
Meanwhile, the future Queen has invited two of her own exes – Rupert Finch from her first year at St Andrews and Willem Marx, with whom she is thought to have shared a teenage romance at Marlborough College.
Other surprises on the guest list have come with the inclusion of the Middleton family’s friends from Mustique where they often holiday.
Basil Charles, extrovert owner of Basil’s Bar and the island’s head tennis coach Richard Schaffer will be both be at the most exclusive wedding of the year.
When the lights go down at the Palace, the island crowd will join the couple’s school and university friends, members of the Middleton family, (Kate's parents have invited 100 guests), William’s Gloucestershire pals and, of course, his loyal personal staff, who’ve prepared every last detail of the wedding with such care.