They actually did it:

Ed Miliband's stone slab. Labour says will be put up in Downing St garden if they win pic.twitter.com/sQ44clVtYq

— lucy manning (@lucymanning) May 3, 2015

“If I am prime minister, I will keep our stone in a place where we can see it every day as a reminder of our duty to keep Labour’s promises.”

Arrrrrrite!