As an Oxford undergraduate, required to be in residence for just three eight-week terms a year, I was reasonably well off. But as a research student I had to finance all my travel and other expenses, plus my year-round board and lodging, out of a modest quarterly subvention of £125 (around £600 per month at present values). My bank balance was never very healthy. So an invitation to a free dinner was something I could not bring myself to refuse.

In the autumn of 1967 I received just such an invitation. This took the form of a letter, hand-written (as I recall) by William "Bill" Deakin, the founding Warden of St Antony's College. I was invited to partake of dinner, at the college, with him and what he described as a 'colleague.' Of course I knew Deakin by reputation – he was an historian who had been Winston Churchill's literary assistant and who had undertaken special operations in Yugoslavia during the Second World War. But St Antony's specialised in international relations, whereas my research (supervised by "Pat" Thompson, a former Bletchley Park code breaker) was in modern British history. What on earth could Bill Deakin want with me?

At the dinner (and a lavish dinner it was too, expensive smoked salmon washed down with copious quantities of beer and spirits) I found out. Or at least I think I found out. I was plied with questions. What languages did I speak? Did I enjoy foreign travel? Eastern Europe? South America? Did I have any current girlfriends (I had none)? Or did I prefer male company?

It was only over dessert (accompanied by an excellent Drambuie) that the penny dropped. It should of course have dropped much earlier. There is no such thing as a free dinner. Bill Deakin had strong connections with the Secret Intelligence Service (popularly known as MI6). The entire purpose of the dinner was to "look me over" with a view to my being recruited as one of Her Majesty's spies. As I downed a second Drambuie I knew I had to make a quick decision. "Bill," I said (for he insisted on my calling him thus), "I don't want the job you may be thinking of offering me." He neither confirmed nor denied the truth of this statement. Ever the gracious host he told me how delightful it had been to meet me. And that was that.

I sometimes wonder whether I had been over-hasty in bringing this stimulating relationship to such an abrupt end. I can tell you now that what raced through my mind, as I savoured that second Drambuie, was whether spying was a proper job for a Yiddisher boy. Would my parents approve? I decided, on the spur of the moment, that it wasn't and they wouldn't.

The entire purpose of the dinner was to 'look me over'

Was I right? After all, didn't Moses send spies to reconnoitre Canaan? Jews in the Diaspora have often acted in intelligence-gathering roles - not always on the winning side, it has to be said, and not always with successful or praiseworthy results. But in his book They Dared Return the historian Patrick O'Donnell tells a thrilling if tragic yarn of Jewish spies who worked behind enemy lines in Nazi Germany. One of my Oxford teachers – Isaiah Berlin – though not strictly speaking a spy, continued working in the Zionist interest while attached to the British diplomatic mission in the USA in the early 1940s. The late Dayan Michael Fisher, who virtually established the Beth Din of the Federation of Synagogues, told me (in the course of my researching the Federation's history) that he had actively spied for the British government during the 1940s, reporting on the activities of Communist-inclined Jews and translating from the Yiddish the contents of intercepted letters. And I need hardly add that the exploits of the Mossad – Israel's intelligence agency – are legion, and legendary.

As a university teacher I am naturally asked to give references on behalf of former students. One day there arrived at my office a man dressed in the customary shabby raincoat who proceeded to ask me searching questions about a student whom his Whitehall-based "company" was thinking of employing. The student I knew to be Jewish; to my astonishment, the man in the shabby raincoat confessed also to being "of the faith".

But on balance I'm inclined to think I was right to have declined – in the national interest, you understand - the offer Bill Deakin never quite made to me.