Mark Strong as Conor Cruise O’Brien: another screen-Irish accent

There are several reasons to see The Siege of Jadotville in cinemas. It's a damn fine action film. It pays overdue respect to the Irish soldiers who fought bravely with the United Nations in the disturbances, in 1961, in what is now the Democratic Republic of Congo. And then there is the prospect of seeing Mark Strong – more usually a polo-necked assassin or sleek spy – playing dusty, tweedy Conor Cruise O'Brien.

Strong always takes control of a character. But what’s up with that accent? This is a tricky one. The late Cruiser spoke in a patrician rumble that straddled the thinnest point of the Irish Sea. One senses Strong, raised in north London, constantly teetering between one thing and the other.

Still, he does all right. Just think how many awful fake Irish accents you still detect in the movies and on TV. A quick poll on an avian-themed social-media network generates a host of suggestions.

Tom Cruise's aural atrocity in Far and Away – what a Lucky Charms box might sound like if it were soaked in Irish Cream and served with cabbage – is, perhaps, still the most notorious manifestation. Less forgivable still is Kevin Spacey's symphony of begorra in Ordinary Decent Criminal. Aren't you supposed to be one of your generation's greatest actors, Kev?

If you want to hear a contrast between how it should and shouldn't be done then listen to the cacophony of immigrant voices in the current remake of The Magnificent Seven. Mark Ashworth, who was born in Manchester but raised in Tennessee, does a damn fine job as the Preacher. The other "Irish" all speak in that strange, tortured oscillation that, crucially, belongs to no particular part of the country (or planet).

It's that lack of specificity that makes standard patronising twinkle (SPT) so infuriating. Brad Pitt's bad accent in The Devil's Own is, to be fair, recognisably a bad Northern Irish accent. But where did Gerard Butler – a master of SPT – think his character was from in PS I Love You?

Jamie Dornan, raised in north Co Down, worked hard at a Co Kerry accent to play Comdt Pat Quinlan in The Siege of Jadotville. Leo Quinlan, son of the late officer, sounded sincere when, speaking to me, he was polite about the resulting vowels.

In contrast Pierce Brosnan, a native of Navan, resorted to pure SPT when playing Desmond Doyle in the worthy Evelyn.

Big hats with buckles on them

So where does this strange nonaccent come from? This is not how Irish people speak. This is how Americans would like Irish people to speak. The sing-song lilt argues for magic, poetry, romanticism and all those other things that distinguish us from people who rarely mend shoes while wearing big hats with buckles on them.

We must bear some responsibility for this phenomenon. You get stage Irish in the melodramas of Dion Boucicault. Christy Mahon in The Playboy of the Western World is the model for 1,000 "crafty" Irishmen who followed in his wake.

The local hero who must take most responsibility for the proliferation of that strange accent is, however, the peerless comic actor Barry Fitzgerald. From south Dublin, Fitzgerald was deliciously versatile – he could be hard as nails when the part required – but we still require him to answer for the unavoidable Fr Fitzgibbon in Going My Way (incidentally, the only role ever to generate an Oscar nomination for both best actor and best supporting actor).

Of course, Fitzgerald sounds properly Irish when dying bravely while Bing Crosby sings Too Ra Loo Ra Loo Ral. You would, nonetheless, have some trouble pinning the accent down to a county. This clever actor knew how American audiences wanted Irish priests to sound, and he gave them just that. He gave them some more in The Quiet Man. Here are the urtexts of SPT.

Never mind. With the assistance of excellent dialect coaches such as Brendan Gunn, overseas actors have got steadily better at proper Irish accents. Kate Hudson did perfect posh Dublin in Gerard Stembridge's About Adam. Young Will Poulter did note-perfect Northside in Gerard Barrett's recent Glassland. Cate Blanchett's accent in Veronica Guerin was better than the film that surrounded it.

Maybe, rather than worrying about the lingering traces of SPT, we should be fretting about foreign anglophones taking our actors’ jobs. Isn’t this what they call cultural appropriation? I’m sure Irish actors would happily forgo all those big gigs playing Americans and Brits in hit series and marquee blockbusters if outsiders promised to stop playing Irish people.

Leave Taken to the Rock. Leave Fifty Shades of Grey to Justin Timberlake. Hang on. Maybe that isn't such a good idea. Let the thespian cross-pollination continue with ever-greater vigour. But mind your vowels.