CHRIS KOENIG looks at the life of Sir George Downing, who was an ally of Cromwell then Charles II at Oxford

Among the assembled dignitaries at the fourth Parliament called by that wily old monarch Charles II in Oxford's Bodleian Library was Sir George Downing, after whom the Prime Minister's residence in London is named.

In an amoral age of fiercely shifting allegiancies, he stood out as a particularly barefaced turncoat. During the Commonwealth he acted as Cromwell's adviser on foreign affairs with a special mission to try and bring about a sort of European union of all the Protestant powers.

Included in his foreign activities of course would have been the job of harassing poor, poverty-stricken Charles II from state to state during his years of exile, under the direction of Cromwell's feared spy master John Thurloe.

Extraordinary therefore to see Downing not only at the king's side in Oxford at the restoration, but created a baronet too.

The trick he pulled was to put his contacts and skills acquired under Thurloe at the king's service. He started hunting down those so-called Regicides - the 59 people who had signed the death warrant of Charles I - who had fled abroad at the Restoration.

One he failed to catch was Sir Edmund Ludlow, a former student of that particularly Royalist college, Trinity, Oxford, which had been one of the first to offer up its silver to be melted down and spent in the Royalist cause of Charles I. He died in Vevey, Switzerland, after writing his memoirs which are now valuable for historians.

John Thurloe, we now know, was allowed to live out his life near Great Milton thanks to secrets he knew concerning the king's own Catholicism. In this he had the advantage over another Oxfordshire regicide, Adrian Scrope, of Wormsley, who was hanged drawn and quartered.

In any case, this Oxford Parliament was the last that Charles II called. Thereafter he managed without, thanks largely to a secret financial deal with his cousin Louis XIV, agreed at the secret Treaty of Dover, under the terms of which the French king paid him money in exchange for guaranteeing the Catholic succession.

He felt secure enough in Oxford to sit on his throne in Convocation House and pronounce: "I have the law and reason and all right-thinking men on my side; I have the Church (pointing at the bench of bishops) and nothing will ever separate us."

Tory Oxford, of course, supported the succession of Charles's Catholic brother James, as opposed to his son Monmouth, whose legitimacy was the subject of much debate. Sitting in 1683, two years before the death of Charles II, the Convocation of Oxford University declared against authors of pro-Monmouth books and leaflets, describing them as "false, seditious and impious, and most of them . . . also heretical and blasphemous". It declared itself against "certain pernicious books and their damnable doctrines".

As for Sir George Downing, his greed and treachery made him unpopular with almost everyone with whom he worked. But he was a past master at seeing where the shifting political sands were heading and flattering the right people.

But does the fact that he endowed a college in Cromwellian Cambridge rather than Royalist Oxford indicate where his true feelings lay?

As for Downing Street, where prime ministers and chancellors of the exchequer have lived since the early 18th century, Sir George built it. He was a speculative builder as well as an opportunist politician.