BritishinformalVery quickly or eagerly:I shot up the ladder like a rat up a drainpipe...
If it had been a victory, Craig would have been in there like a rat up a drainpipe to make sure he got full credit and lots of pictures in the local paper.
Give him an opening and he's in there, like a rat up a drainpipe.
If he sells the bank, which he has said he will do, then she will be on to him like a rat up a drainpipe.