GIVE BLOOD: Today's sanguineous extrusion points are at the Bishopsgate Institute (9.45-11am and 1-4pm), the Hop Exchange on Southwark Street (11am-1.30pm and 3-5.30pm) and the Kilburn Marriott (12.45-3pm and 4.30-7.30pm). Free, just turn up.
PHOTOGRAPHY: The London Photo Festival begins today, running until Saturday in the Crypt of St George the Martyr, opposite Borough Tube. The show provides an opportunity for amateur or semi-professional photographers to exhibit their work, and for everyone else to snap up some snaps. Free, just turn up, 10.30am-8pm
AFFORDABLE ART FAIR: The annual £40-£4,000 Affordable Art Fair opens in Battersea Park. Over 100 galleries are represented. £10, 11am-9.30pm
HAPPY BIRTHDAY TO US!!: Londonist is exactly 8 years old this morning. The very first sentence to be published? "Islington Council has installed specially constructed benches for its resident hardcore street drinkers." Read on. 10.17am
FREE LUNCH: We've no idea if the book's any good, but if you go to Waterstones Piccadilly today, on the first floor you can enjoy a literary lunch to mark the launch of Eduardo Halfon's The Polish Boxer. Free, just turn up, 1pm
BEER FESTIVAL: Book the afternoon off work and head down to Wandsworth Common, where the Hallowe'en Beer Festival includes 100 beers and 25 ciders for you to sample (responsibly). £4, just turn up or book online for priority entry, 1-11pm
ART CRAWL: Last Thursday of the month means Fitzrovia Lates, an evening in which the myriad galleries of that district open late and put on a show. See a list of participating venues, as well as details of talks and tours. Free, just turn up, 6-9pm
FEARS: Imperial College puts on a special Hallowe'eny evening devoted to the science of fear. Pop in, if you dare, for talks and activities about anatomy, zombies and the possibly scary future of artificial intelligence. Free, just turn up, 6-9pm
FEEL THE UNIVERSE: Meanwhile, Imperial's Astrophysics department explores how the cosmos can be felt, smelled, heard and tasted, as well as seen. The mind boggles. Free, prebook, 6.30pm
DICKENS: The Idler Academy in Westbourne Park Road requests your company for an evening of Dickens impersonation, in the company of Sir Tim Ackroyd and John Tallents. £20, 6.30pm
MIDDLE EASTERN FILM: Future Shorts Festival and the Edge of Arabia exhibition pool talent to bring you an evening of short films from the Middle East, projected among Islamic and Arabic art work. Music and food complete the #cometogether event at the Old Truman Brewery. 7-10pm
RATS: Treadwell's Bookshop in Bloomsbury hosts an event exploring the myths and activities of rats, including a magic spell to get rid of them. All a bit odd, but that's Treadwell's. £6, just turn up but get there early as this one's had more press than most events at this venue, 7.30pm
COMEDY: A few tickets remain for Dara O Briain's show tonight at Hammersmith Apollo. £25, 8pm
SCARY OPERA: Improvised comedy horror opera to a silent film? We've no idea what to expect from Fright at the Opera in Kings Place, but it sounds splendid. £14.50, 8pm
Random London Trivia Of The Day
The O2 Dome was built, of course, to mark the celebrations surrounding the turn of the Millennium, and purposely sited next to the Prime Meridian to give it a chronological legitimacy Less well known are the symbolic dimensions built into the structure. The diameter of the Dome (including external supporting elements) is 365 metres, one for every day of the year. It is supported by 12 yellow support towers, one for each month of the year, or hour on the clock face. It's also 50 metres to the top of the canopy, 100 metres to the top of the towers, and almost precisely a kilometre round the edge of the canopy.
London continues its depression beneath nepheloid skies, yet there may be gory horrors ahead For Hallowe'en. The BBC reports the possibility of 'blood rain', a phenomenon where dust mingles with precipitation to produce a rust-coloured downpour.
Secret Hidden False Rumour Of The Day
Holland Park is named after Jools Holland OBE. Features of interest include a boogie-woogie bandstand and the Hootenanny peace gardens.