Carrying a copy of the Financial Times, with a hole in the front cover - presumably so could travel ingonito and still peer at fellow commuters - she Tweeted "Forgive me for being a brat:-after 17 years & yesterday's 2 hrs of traffic-lets save time & money-the tube".
Quite why she bothered remains a mystery, when walking between Piccadilly Circus and Leicester Square would have saved her even more money.
Feeling "liberated" by the experience and since not travelling Underground for almost 20 years, Halliwell tweeted a couple of Tube tips for those of us not used to a daily commute.
"Tube tip – doors stops at platform entrance, or below sign, more seats at end carriage. oh & it's not smelly just saying."
"Rules of the tube, I notice no one smiles or looks at each other, like stay out of my zone."
It's almost as though Ms Halliwell felt she'd be travelling on a whole new system from when she last took the Tube. One where those of us who don't have a daily commute of 40 minutes or more, or have the luxury of an empty carriage, feel the need to smile at each other.
Fellow Spice Girl Emma Bunton who co-presents the breakfast show on Heart was challenged by Jamie Theakston to use the Tube this morning when she revealed she hadn't used the system for 15 years.
Bunton has some problems swiping her Oyster card and said: “I got an Oyster card and as soon as I put it down, it said ‘seek assistance’. I started saying hello to people but no-one was having any of it.”
She added: “I know everyone has to do it in the mornings and the rush hour in the afternoons and it’s a toughie, but I enjoyed my moment.”
I'm worried that Victoria Beckham might decide to follow in the footsteps of Emma and Gerri and Tweet about how Tube travel plays havoc with her bunions. Or how no one noticed her travelling in her shades and just returned her pouty look with an equally dark Paddington stare.
Will there be more of a trend of A list celebs travelling on the Tube now if only to give them something to Tweet about which make them seem like "normal Londoners"?
For my part, I get more joy out of spotting celebs like Alex Kingston, Roland Gift and Justin Lee Collins on the Tube. They don't see Tube travel as a special event or a moment to be enjoyed. Like the rest of us commuters, they just look bored or end up staring into space hoping there won't be any delays or random people trying to strike up a conversation with them.