Higgins’ books were populated by a rich cast of colourful characters, some heroes but more often anti-heroes, at least to begin with, who were no strangers to violence and could handle themselves in a rough house, and were skilled at handling weapons, fast boats, aeroplanes and scuba-diving equipment. They may have dabbled in gun-running or smuggling, be washed-up pilots or whiskey-priests, ex-IRA gunmen, former soldiers or sailors down on their luck seeking one last chance of a quick fortune or a last shot at redemption. Whatever their background and their motives, they would come good and do the right thing in the end, usually revealing a rather romantic sensitivity along the way – especially when there was a damsel in distress.

Yet for thriller readers, and cinemagoers, the dominant flavour of the 1960s was the spy story, from the fantastical escapades of James Bond and his many imitators to the more downbeat and cynical accounts of spies and spying as documented by John Le Carré and Len Deighton, and on television by James Mitchell’s Callan.

Jack Higgins was not slow to recognize the trend, and in 1962 – the year Dr No hit the cinemas and The Ipcress File the bookshops – he launched the career of the half-English, half-French secret agent Paul Chavasse in The Testament of Caspar Schultz. A much-underrated recruit to the Sixties’ panoply of fictional spies, Chavasse’s first published assignment saw him on the trail of a Nazi war criminal, one of the most popular thriller plotlines, not just then but for many years after.

For whatever reason, Higgins did not extend the fictional life of his secret agent beyond 1969, by which time he had also turned his restless pen to the crime thriller, with a new hero, and his first protagonist to be a serving British policeman – Detective Sergeant Nick Miller.

Not that the three novels in the Nick Miller trilogy, published between 1965 and 1968, were the sole focus of Higgins’ creative energy. Far from it, as in the same period he produced seven other novels of secret agents, rogue gunmen and high adventure under his various pen-names, a quite remarkable achievement for an author who had not yet given up ‘the day job’. (It was around this time that he ran into a friend he had not seen for a while who greeted Higgins with: ‘Are you working – or just doing the books?’)