The big travelling crane they've just built at the Crossrail dig opposite has been running along its track today - it goes from about 100 yards from the left of my house to 50 yards or so to the right, I think. I don't think that it is fully operational yet - it seemed to be moving slightly jerkily, I think that they are still adjusting it. At a guess it's about 30ft high and 60 wide - diffictult to tell since there isn't much to give a sense of scale in either picture - over an excavation that's already fairly deep and will be getting much deeper.
Here are a couple of pictures of it as it went by.
The second is a little blurry, I was using zoom through a glass window - when it's a little warmer I'll take some pictures with the window open.