Today marks the thirtieth anniversary of the Downing Street Declaration – one of the key building blocks of the Northern Irish peace process which led to the Belfast Agreement of 1998. That accord, forged between prime minister John Major and the taoiseach Albert Reynolds, is widely held to be a masterpiece of calculated ambiguity.

In a memorable turn of phrase, the British government acknowledged that it had ‘no selfish strategic or economic interest’ in Northern Ireland – a formula first employed in Ulster secretary Peter Brooke’s Whitbread lecture of 9 November 1990.