Things To Do In London Today: Tuesday 19 February 2013

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GIVE BLOOD: You've got three opportunities to donate blood today (although they'll only let you do it at one)...St James's Square, Bishopsgate Institute, and Perseverance Works on Kingsland Road. Free, just turn up, check site for times

PHOTOGRAPHY: It's 20 years since War Child was founded to help children in war zones. A new exhibition at the British Music Experience (in the O2) shows previously unseen photos from War Child concerts. Street artist Slinkachu has also contributed a few of his small-people creations to the exhibition. £13 (general entrance fee), just turn up, until 28 March 2013

MATHS: Did you know that the average person has fewer than two legs? Find out more screwy stats as Raymond Flood considers the misleading world of means, medians and modes in a Gresham lecture at the Museum of London. Free, just turn up, 1pm

BIG COX: The ever-popular Brian Cox gives this year’s Michael Faraday Prize Lecture at the Royal Society, discussing how we can make Britain the best place in the world to do science. As usual, the RS operates its ticketless first-come, first-served policy, which is smashing for lesser speakers, but a real pain in the hadrons for big occasions. Be sure to arrive early, and be prepared to queue if you want to get in. Free, just turn up,5.30pm

DECEPTION: The second Museum of London Gresham lecture of the day explores ways — mechanical and through body language — to detect when someone’s lying. Free, just turn up, 6pm

BOOKS: Jim Crace talks about Harvest, his last novel before he retires, at Foyles. Free, prebook, 6.30pm

SOCIOLOGY: Anthony Giddens gives a public lecture Off the edge of history: the world in the 21st century at Sheikh Zayed Theatre, LSE. Free, just turn up, 6.30pm

POETRY: Niall O’Sullivan hosts the Poetry Cafe‘s weekly open mic night. £5, just turn up, 7.30pm

TUBE: Max Roberts, master craftsman of alternative Tube maps, is giving a talk tonight at the Design Museum. The seemingly exorbitant ticket price includes entrance to the museum's gallery's before the talk. £17, prebook, 7.30pm

COMEDY: Last week’s podcast guest Chris Coltrane hosts his friendly monthly politics night at Camden’s Black Heart, with guests Josie Long, Adam Larter and Mark Stephenson. £3, just turn up, 8.30pm

GIG: Exclamation Pony is the side project of Ryan Jarman from The Cribs. Expect shouty fun with unexpected subtleties at Hoxton Square Bar and Kitchen. £10.60 + bf, prebook, 8.30pm

Random London Fact of the Day

The River Walbrook was the first of London's ancient rivers to be buried beneath the city. It runs from Shoreditch down to the Thames, carving the valley between Ludgate Hill (St Paul's) and Cornhill (Leadenhall). Today, it's part of the sewer system, but you can still see where it (should) meet the Thames during storm conditions. At low tide, go down the steps next to Cannon Street Station and head west past the moored, rusting hulks on the foreshore. Voila, this blocked-up portal. Poet Tom Chivers is currently leading 'pilgrimages' along the Walbrook valley. They're all booked up, but you can find out more here.

Good Cause of the Day
What's more thrilling than shooting the rapids? Shooting the rapids in the dark. CLIC Sargent, a charity supporting children with cancer, is organising an evening of fun and splash at the Lea Valley White Water Centre this autumn. Participants get to complete the Olympic course four to six times between 8pm and midnight on 6 September 2013. It's a team event, with nine people per raft, so get mithering your work mates now. To enter, you'll need to pay a £20 entry fee and raise a minimum of £150 for CLIC Sargent. All equipment will be provided for you, and absolutely no experience is necessary. Sign up here.

London Weather
For the sake of novelty, we were toying with writing today's weather in verse form. Trouble is, there's not much that rhymes with "early fog, clearing later to reveal blue skies that will remain all afternoon". We tried "Burly frog, swearing gator to conceal two pies that will detain your baboon", but that's not the kind of scenario that our core audience would identify with. So, we'll stick to writing in prose.

Early fog, clearing later to reveal blue skies that will remain all afternoon.

BBC Weather, is just way better at this forecasting lark.