By Greg Cochrane
Newsbeat music reporter
Florence Welch closed her set with a cover of You've Got The Love
It's a wonder the steel perimeter fence doesn't bend before it gets opened, such is the crowd's hunger to get on site on the first day at Lydiard Park.
Once the gates do fly open the first sound 20,000 punters are treated to is DJ Tim Westwood greeting people like the gentlemanly hip-hop host: "Wiltshire, let me hear some noise for the Big Dog," he hollers. They reciprocate.
Just as rumbling are In New Music We Trust openers Fightstar, whipping through their brand of hard and coarse emo-punk. So hard and coarse in fact that coming offstage Charlie Simpson shows off a set of bleeding fingers. Dedication.
Meanwhile Fightstar guitarist Omar, like most of the men here, is more interested in 'checking out' what The Saturdays are like.
The girls themselves, opening the main stage, do an admirable job of kicking Big Weekend off in glamorous, perfumed-pop style.
Their dance moves might by impaired by the height of their shoes but The King Blues have no similar problems.
The Saturdays added an element of girl-band glamour to the day
The London threesome [fleshed out to six live] show real energy as they blitz through a cheeky set of ska-punk rock.
They even have the audacity to cover Dizzee Rascal's Bonkers in their own stomp-fashion before the rapper has a chance to play it himself.
Mate of the band, and later highlight of the BBC Introducing Stage Master Shortie [aka 19-year-old Theo Kerlin], joins them on final song I Got Love.
It's a closely fought battle between Southend throttle-rock bods Baddies and Florence And The Machine for smartest band in this field today.
But Florence wins out, as she models a ribboned black cocktail dress and her backing band matching glitter chain mail.
The general effect is like Strictly Come Dining meets Fantasia - as Florence Welch herself rolls on the floor, her shrill voice trilling in the early afternoon air.
Spectacularly, she wraps up with a cover of Candi Staton's You Got The Love and dives into the crowd still with a pair of five inch stilettos on. Can't be safe.
Next up, Deadmau5 - aka Canadian producer and DJ Joel Zimmerman - is this weekend's best kept secret. He rides onstage using a green BMX wearing a customised disco-ball mouse head. Yes, mouse head. Which makes Calvin Harris' spangly glasses look like a budget effort.
Deadmau5 takes the prize for best on-stage outfit on Saturday
His hard-dance set crunches together Muse's Knights Of Cydonia with Daft Punk's Harder Better Faster Stronger and his own material.
It's a tough call for the dance heads as 2 Many DJs provide stern mid-afternoon competition by pulping those at the Outdoor Stage at the same time with some savage cut 'n' paste mixing.
Back at the INMWT arena St Albans' Friendly Fires are weary. Today is officially the final date of what seems to the like an ever-lasting tour for them.
Yet they conjure the magic for one final time and still manage to bring the party with their now trademark calypso drumming and feathery go-go dancers.
London cherub-faced indie-boys Bombay Bicycle Club are surely destined for bigger things than the BBC Introducing Stage, but late in the afternoon they provide a taught 20 minutes of charming indie.
Following that, Australians The Temper Trap do what special bands do, start with an empty tent and end with a full one. Lead man Dougy's ghostly voice transfixing those converted.
There's an air of predictability about Dizzee Rascal's set on the main stage.
20,000 now sun-kissed Swindonites are positively willing [by going absolutely mad when it's played] Bonkers to be this weekend's anthem - and it doesn't fail.
Kasabian's Tom Meighan shows off a new look on the main stage
After bringing on a coy Calvin Harris for Dance Wiv Me, Dizzee unleashes a bass-heavy version of his banger. Swindon would be in awe if it wasn't too busy climbing tent poles with excitement.
Back over on the INMWT stage Doves, through no fault of their own, seem comparatively tame.
After six months in the studio, Kasabian's Tom Meighan has undergone a transformation - tonight he looks like Obi Wan crossed with ex-Arsenal player Emmanual Petite with his camo jacket and hair tie.
Fortunately their new sound is better than their new look. Fire, augmented with a fleet of backing singers, sounds huge. As does Vlad The Impaler and Club Foot.
With Basement Jaxx bringing catsuits, leotards and thunderous bass to the second stage, DJ's Vernon Kay and Chris Moyles introduce Big Weekend's first day finale: Snow Patrol.
55 minutes of hold-a-stranger-by-the-hand warmth ensues, with the ever charming Gary Lightbody conducting proceedings like a friendly neighbourhood vicar.
Stand out moments Chasing Cars, Run and Final Straw wrap Swindon up in a summer-rock blanket and send them home glowing.
With Lily Allen, The Enemy and The Prodigy still to come on day two, things might just get even better.