Royal wedding 2018: The reception video you weren't meant to see

It's the video that offers an inside glimpse into one of the world's most exclusive parties.

Shot by Jessica Mulroney's makeup artist Rachel Renna, the short Instagram clip shows Meghan Markle's close friend milling with other guests before heading to the second royal wedding reception.

Mulroney channels old Hollywood glamour in a gold sequin dress, and the stylist's husband Ben Mulroney looks dapper in a classic tuxedo, news.com.au reported.

Toasting glasses of champagne, the Canadian power couple and other guests appear in high spirits as they prepare to head to the second, more exclusive celebrations at Frogmore House.

Hosted by Prince Charles inside a $600,000 glass marquee, only 200 wedding guests were invited to the night party, which followed the ceremony at St George's Chapel and an afternoon reception at St George's Hall.

Guests were instructed to "dress to the nines" for an evening of "old-fashioned glamour and gallons of champagne", the Sun reported.

Inside glimpse at pre-reception party. Photo / Instagram

All 600 guests had been issued a seven-page etiquette booklet before the wedding, with strict instructions to "surrender" mobile phones upon arrival, the Daily Mail reported.

However, Meghan's celebrity friends such as Mulroney, Priyanka Chopra and Serena Williams appeared to have bent the rules by posting photos and videos of themselves to Instagram between the festivities.

At the evening reception and away from the prying eyes of the public, Prince Harry and Meghan's friends weren't afraid to let loose.

According to the Sun, Meghan's BFF Williams put her tennis playing skills to good use, schooling guests on US drinking game beer pong.

Serena Williams was reportedly queen of beer pong at the after-party. Photo / @alexisohanian Instagram

Actor Idris Elba hit the turntables and turned DJ, bringing the house down playing soul, 1960s R & B and 1980s dance hits.

The Sun reported that the wedding reception soon turned into a party atmosphere, with a royal dance-off.

Actor George Clooney took Meghan for a spin on the dancefloor, followed by Kate Middleton.

Comedian James Corden instigated an extraordinary dance routine, which featured Prince Charles, Prince William and Prince Harry.

Newlyweds Meghan and Harry hit the dancefloor to I Wanna Dance With Somebody.

"James ­Corden did his best to entertain and it went down an absolute treat," a source told the British newspaper.

"He even compered a dance-off between Harry, Charles and William."

Prince Charles, who left the festivities at 10.30pm with wife Camilla, also ensured guests were well fed and had plenty to drink.

"There were burger bar stalls, whiskey bars, candy floss, games to play, acts performing and a DJ with a dance floor," a source told the Sun.

"There was a gin vermouth cocktail created for Charles and Camilla, who are massive gin fans apparently."

Harry and Meghan's guests let their hair down at the evening reception. Photo / Getty

Those still standing after the joyous, but long wedding day, could at least ease out of their stiletto heels after being given monogrammed slippers at the reception, which ended in an explosion of fireworks at 2am.

Then there was an after-party at Chiltern Firehouse, a late-night hot spot in Marylebone, owned by the groom's pal, Andre Balazs. Pretty Little Liars actor Troian Bellisario, the wife of the Duchess' Suits co-star Patrick J. Adams — was a fan of the slippers on offer.

"How amazing is this? Because these shoes have come off, they have slippers for us. Slippers," Bellisario wrote on Instagram.