Northern Ireland First Minister Peter Robinson: "She was undoubtedly one of the greatest political figures of post-war Britain and she changed the face of our United Kingdom forever.

"As our first female prime minister, she made history and as 'The Iron Lady' she was at the frontline of winning The Cold War as well as ensuring the freedom of the Falklands Islands.

"Whilst we disagreed over the Anglo-Irish Agreement, Mrs Thatcher was committed to the union and later described the Anglo-Irish Agreement as one of her greatest regrets."