WOOLLY HAT DAY: Broadgate Circus will be home all day to hundreds of woolly hats, knitted for St Mungo's charity by the public. See the hats, talk to the creators, join in the yarnstorm. Free, just turn up, 7am-7pm
ART: The Affordable Art Fair continues in Battersea Park. £12/£10, 11am-6pm
GORY CAKES: St Bartholomews Pathology Museum in Smithfield holds a three-day fest of gory cakes shaped like human body parts. A series of lectures will run alongside. Runs till 28 October. Free, just turn up, 11am-6pm
WINTER SPORTS: The two-day Freeze Festival opens at Battersea Power Station. As well as snowboard and skiing action, enjoy live music from the likes of DJ Shadow and Public Enemy. £44, 12-10.30pm
WILL YOUNG: Join the pop star at Waterstones Piccadilly for a literary salon in support of his new memoirs. £6, just turn up, 12.30pm
DAWN FRENCH: The comedian and actress talks about her new novel with Sue Perkins at the Criterion Theatre. £15, includes a signed copy of the book, 6pm
LATE ART: Guildhall Art Gallery holds one of its occasional (and always wonderful) late openings. London-inspired music, a giant drawing of the recent riots, archive London films in the Roman amphitheatre and, of course, plenty of impressive art. Free, just turn up, 6-10pm
FREE COCKTAIL: Anise bar relaunches in Devonshire Square, near Liverpool Street, tonight. You can claim a free cocktail by saying "Calcutta Cuppa" to the door staff. Just turn up, from 6.30pm
OTHER LATE OPENINGS: As usual on a Friday, the British Museum is open till 8.30pm, the National Gallery and National Portrait Gallery stay awake until 9pm, while the two Tates, the V&A and Royal Academy are dirty stopouts until 10pm. All free and just turn up
MUSIC: Candy Flossing presents unique, alternative, young up-and-coming British music and cabaret in the Roundhouse Studio, Camden Town. £5, 7pm
MUSIC FUNDRAISER: Spark in Corbet Place off Brick Lane is a charity music-fashion-dance event raising money to help Mayamiko, an organisation improving working conditions in Malawi. Have lots of fun, for a good cause. £15, 7pm
DANCE: Watch a double bill by contemporary dance outfit Lost Dog at The Place, Euston Road. £15/£12, 8pm
Random London Fact of the Day
As well as the Woolwich Foot Tunnel (celebrating its centenary today, see above), there are two other places where the public can walk beneath the Thames. Greenwich Foot Tunnel is one, but (for the brave) there's also a footpath through the Rotherhithe Tunnel. Don't try ambling through the Blackwall Tunnels — there is a narrow walkway for emergency use only, but you'd probably get picked up by the security services before you got too far. Historically, you could have also walked through the Thames Tunnel, which is now part of the Overground network, or a long-disused subway between Tower and London Bridge. Wikipedia lists many more transport and cable tunnels beneath the water.
Does anyone recall what the sun looks like? Our lifegiving orb has been absent for so long, its very existence is passing into the realms of folklore and half-muttered superstition. But, lo, what's this? A few breaks in the cloud today should yield a rare sighting of that most elusive astronomical body. Despite the rays, it's going to be chilly, so wrap up warm.
Secretly Hidden False Rumour Of The Day
Londonist is entirely written by an Artificial Intelligence bot called Whittington. A less sophisticated, earlier version writes the Mayor of London's speeches. It regularly malfunctions, leading his press office to hastily rally to invent back-stories for terms like "wiff-waff" and "Geiger counter of Olympo-mania".