Reminds me of one I took a few weeks ago, which I'll link you once voting is over - so I know that you've flipped L&R on this shot :o) You've managed to keep the highlights from blowing out, but boosted it enough to make the tower stand out against the skyline, nicely done. Oh, and it appears we're the only two Gerkin entries, which surprised me!
EDIT: oh wait, you took a shot from the north or east side of the Tower, not the south (ie riverside), so you haven't flipped the image, doh! :o)
The gherkin! I've never been to London, but it seems like a great place to contrast old and new... I think if you had gotten a little lower, you could have removed that distracting blue light just left of center above the castle. Too bad the castle wasn't lit with torches instead of electric lights. :)