You can visit the photoblog and listen to the concert live on Radio 1 from 7-10pm GMT (aka 2pm-5pm EST).
Coincidentally, Brixton Academy was the very first place I ever saw Coldplay. Here is a picture from that April 30, 2001 show:
At the end of the show, Chris lifted up his arm in the air, guitar in hand and then THREW HIS ACOUSTIC GUITAR INTO THE CROWD.
I remember being in a complete panic on the tube ride home to the dorms since the next day around 11am my final 20 page 19th and 20th Century Novel paper was due. I risked flunking out of college for sweet sweet Coldplay. Luckily, everyone else in my class wrote even worse papers than I did, so I squeaked by. (THANKS NEIL VICKERS!)