Will this plug adapter work?

I'm in the UK and have a US plug.

This is the type of plug I have:
image

This is the adapter I'm looking at:
http://www.amazon.co.uk/...000NPACOG/

I'm not sure if it'll work as the adapter has an extra hole as opposed to the 2 which my plug has. The 2 rectangular slots also look slightly different sizes. If that doesn't work, can someone find me one that will?

That will work fine, the third hole is for the ground.