The Irish singer – who is expecting her second child – showed off her blossoming baby bump in a silver T-shirt, teamed with unusual black trousers and grey ankle boots.
We can't help wondering though, is she not freezing with no coat?!
Una and the rest of The Saturdays – Mollie King, Frankie Bridge, Rochelle Humes and Vanessa White – were pictured arriving at the Casio store in Covent Garden on Tuesday night (11 November).
The girls became ambassadors for the Sheen watch collection earlier this year and last night, they performed a private concert for lucky competition winners.
For Frankie, it meant a night off from Strictly Come Dancing rehearsals. As Sats fans know, she is currently competing on the BBC One dance contest and, of course, being supported all the way by her bandmates!
At the weekend, Una tweeted: "Can't wait to watch our @FrankieTheSats shake her thang on @bbcstrictly."
Una, meanwhile, is preparing for a solo gig of her own having landed a role on The Voice of Ireland, the Irish version of The Voice.
The singer will coach alongside Rachel Stevens, Kian Egan and Irish musician Niall Breslin when the show returns to screens in January 2015.
Una said: "I'm delighted to be a part of the fantastic team behind the Voice of Ireland, I love the show and I can't wait to sit in that chair. I know the talent that Ireland has to offer so that button is going to see a lot of action. I'm excited to be working with Bressie, Kian and Rachel but it will be me who finds this year's winner!"
The Saturdays have just released their Finest Selection: The Greatest Hits album but have insisted it doesn't mean the band is coming to an end.
Reveal is now on Google Plus! Join us here for the latest pictures, fashion and celebrity news!
Stars who welcomed babies in 2014!
Copyright: Rex Features WENN/Matthew Taylor/Daniel Deme/Josiah True/Matthre Taylor/Joe