Why take on a study of Winston Churchill and Ireland? I felt that most English people were unaware of the long intimacy of Churchill’s relations with Ireland. It was more profound than that of Tony Blair and Bonar Law who both had Ulster parentage.

Gladstone was heavily engaged with Ireland but this was a late-life phenomenon, while Churchill’s engagement began in his childhood years living in Dublin with his father then an aide to the Lord Lieutenant, and hearing stories of Fenianism.

As a schoolboy Churchill was taken to the Commons to hear Irish debates. After one particularly bitter debate Edward Carson apologised to the teenage Churchill. Churchill gravely replied: “The ship of state, Sir, she sails in troubled seas”. It was at this point that Churchill acquired his sympathetic interest in Parnell about whom he wrote a brilliant essay in 1938 – far surpassing in quality anything written by an Irish politician about an English one.

I felt sure that in London there would be interest in Churchill’s attempt to balance the claims of nationalism and unionism and in the role it played in his activities inside the Liberal and Conservative parties.

In Ireland I knew that there would be there would be significant criticism of Churchill’s record. On those websites devoted to such questions as “Who do the Irish people hate most?” Churchill was a prominent figure. Oliver Cromwell (responsible for the massacres in Drogheda and Wexford) was more unpopular as was Charles Trevelyan (responsible for British policy during the Famine). But Churchill was usually in the top 10 list of the most despised figures.

There is good reason for this. There is Churchill’s use of imperialistic and jingoistic language. More important is his failure in 1918 to come to terms with the shift of Irish public opinion towards Sinn Féin and away from the Irish Parliamentary Party in which Churchill had many close friends, not least Stephen Gwynne who advised him on his Irish history reading. Captain Stephen Gwynne MP also served on the Commission of Inquiry which protected Churchill’s reputation over Gallipoli. As a consequence Churchill regarded the IRA war launched in 1919 as “organised baboonery” and sanctioned, partially successfully, a dirty war against it.

Winston Churchill is presented with a green hat and clay pipe by students during rag week at Queen’s University, Belfast in 1926. Photograph: Topical Press Agency/Getty Images

It is worth adding that Churchill’s belief in the principle of consent in the North is now the conventional wisdom in Irish politics but was rejected by the IRA in 1920-21.

There is the vexed question of Irish neutrality in WWII. Ireland’s position, whilst entirely defensible in terms of realpolitik, is not an heroic tale of moral righteousness

Then there is the vexed question of Irish neutrality in the second World War. It is perfectly fair to argue that the burden of history made this inevitable. The fact remains that Ireland’s position, whilst entirely defensible in terms of realpolitik, is not an heroic tale of Irish moral righteousness. British audiences greatly enjoy Gary Oldman’s rendering of great speeches – “blood, sweat and tears” and so on. They are unaware of the fact that Ireland played a significant part in the Churchill story at this time.

Churchill tried to gain de Valera’s support for the British war effort by apparently opening up the prospect of Irish unity. So desperate was the moment, May 1940, that the Ulster Unionist leadership was actually split on the issue. But Dublin, assuming like everyone else at the time that the German victory was inevitable, said no.

The diplomatic dialogue between Ireland and Germany, in the hands of William Warnock, the Irish chargé d’affaires in Berlin and Joe Walshe, head of the Department of Foreign Affairs, at the time, makes for uncomfortable reading. as Ireland tries to stay on the right side of the Nazis. In the period covered by Gary Oldman’s recent movie The Finest Hour, German files quote Warnock, in a personal comment, during a discussion on the right moment to strike against Britain. saying: “in the last war against Britain that Eire had started the attack too early. This mistake would not be repeated.”

This helps to explain why Churchill in 1943 talks to Anthony Eden of Irish ignominy but, even then, he was well aware of the many Irish contributions to the war effort. Indeed he remained open in principle to Irish unity.

As one who has always been in favour of United Ireland into which the North has willingly entered I would view such an evolution without alarm

When the hardback edition of my book was published the British foreign office archivist, Ted Hallet, generously sent me the text of a telegram to the foreign secretary of September 5th, 1943 in which Churchill said: “There will be no difficulty in resisting the partition argument so long as Southern Ireland stands out of the War. If, on the other hand she comes into the War, great changes of feeling might occur both in the North of Ireland and in the British mind. As one who has always been in favour of United Ireland into which the North has willingly entered I would view such an evolution without alarm.”

There is a sense in which Churchill’s attitude towards Ireland was caught within the framework of the sentimental screenplay he wrote for the film maker Alexander Korda in 1934. William Orange, father of the beautiful Lucy, opposes his daughter’s marriage to a young Catholic; until that is, the young man joins the British army and all contradictions are resolved over a glass of Irish whiskey. The film was never made.

Churchill and Ireland by Paul Bew is out now in paperback from OUP Oxfrod, £9.99