Back at the Foreign Office I used to receive great fat folders seeking my agreement on whether or not the UK should grant licences to our defence companies to export arms to other countries.

These licences cover not just obviously lethal equipment – like guns, missiles, fighter planes – but almost anything associated, including things designed to save lives, like pilot ejector seats, or air traffic controls.

I used to go through these applications with a fine toothcomb. Three other senior ministers were involved too – the defence, international development and trade secretaries. Sometimes there’d be a spirited discussion about the conditions in a country to whom an export was planned.

Every decision was reported to a Commons select committee. Every so often I had to give oral evidence to this committee to explain why a licence had been granted – typically when there had been evidence that the country concerned had been abusing human rights.

Meanwhile the companies involved used to get irritated about the time some of the licence applications took to process.

After the United States, which is in a league of its own, Britain’s defence industries are among the largest in the world. In East Lancashire a huge amount of employment and prosperity depends on multi-national giants like BAE, and Rolls-Royce – and on scores of smaller firms in the supply chain. As we know from the recent redundancy announcements by BAE, when one of these companies sneezes, the whole area can catch a cold.

And our arms’ licensing system is one of the toughest in the world. Although it is supposed to apply evenly across the European Union I was forever worried that another European competitor might not be as scrupulous as we in applying small print of the rules. It’s a very competitive market.

I spent a good deal of my time as Foreign Secretary as an unashamed salesman for our defence industries. So did the Prime Ministers for whom I worked. I’m delighted to see that David Cameron, on his trip this week to the Far East, is batting for the British defence industries too.