An armour-plated "battle bus" used by Margaret Thatcher while visiting Northern Ireland during the Troubles is set to appear at a February 21 auction in the UK.

Margaret Thatcher is popular at auction, with one of her iconic suits selling 1,233% above estimate at Christie's in 2012

Weighing a monstrous 28 tonnes, the bus is thought to have carried the former prime minister in the 1980s. It was later used to transport troops, according to the auction house, which has given it a £12,000 ($18,624) high estimate.

With the bus thought to be chemical, biological and nuclear proof, auctioneer Jonathan Humbert commented: "This isn't a good-looking vehicle by any stretch of the imagination - but it is of social and historical interest. An irreplaceable one-off! An iron bus for the Iron Lady!"

Paul Fraser Collectibles has two great signed photographs of Margaret Thatcher, as well as superb examples of her autograph on card.