Tony Crosland’s The Future of Socialism appeared in 1956, just before the Suez debacle sounded the death knell on unilateral adventurism in Britain’s foreign affairs. That insane episode came to a sudden stop when the White House obliged Prime Minister Anthony Eden to call off his misbegotten military action for fear of financial consequences for the UK economy. The lesson should have been crystal clear: the ‘Age of Empire’ was over and Britain could no longer get far internationally without a strong economy and the support, or at least the understanding, of key friends, partners and allies.

But that lesson had been only partially learned by the time that Tony Crosland became British Foreign Secretary in 1976, when the UK economy was again struggling with problems provoked by the consequences of Suez: a great hike in the world oil price by the Organization of the Petroleum Exporting Countries (OPEC). British diplomacy was still very much about national interests, and the Foreign Office applied its craft in the same way as it had done for generations. But that became increasingly unsustainable as the globalised economy developed. Freight containers, bulk carriers and satellite communications transformed international trade. Jumbo jets supplanted ocean liners and made mass overseas travel affordable. The internet facilitated unimagined new connections. But in parallel came new threats: climate change, cross-border crime, unprecedented levels of migration, population growth, global poverty, pandemics, international terrorism and cyber-attacks. To that lengthening list has now been added the growing threats of food and water shortages. Together there are all the ingredients for a ‘perfect storm’ to hit humankind.

The days of go-it-alone have gone. Welcome to the world of ambiguity and compromise where the art of coalition building is a key skill. Where ministers search for partners in European Council meetings at the Justus Lipsius building in Brussels, the slowest speed-dating club in Europe. Where every balanced package sends out a mixed message and where, when you reach your final destination, it feels like a halfway house. Where a dual-sourced, twin-track, copper-bottomed guarantee could contain a get-out clause in the small print, making it worth its weight in mould. Where an ability to combine a straight face with a white lie could get you noticed. Where dinosaurs and dodos died out but diplomats survived: so many shades of grey in today’s Foreign Office colouring book.