The parents of Tony Whitecliffe (Tommy Steele) have just returned from the small, oil rich country of Ritalla where they have secured a deal to supply them with cattle from their estates. That's not all the Duke and Duchess have planned, as they hope to marry Tony off to the Princess Maria (June Laverick), except they cannot get him interested in her - he'd rather talk about the cows. There's a reason for that, and that is that the parents don't know their son is already married, a fact he is keeping secret from them, so how can he get out of going to Ritalla with anything but the cattle deal on the table?
Tommy Steele was Britain's first rock 'n' roller, and for his first film they had put him in a biopic where he sang extensively. He sung just as much in the follow up, a trifle concocted by songwriters Lionel Bart (later of Oliver! fame) and Mike Pratt (later of Randall and Hopkirk (Deceased) fame) for the team who had begun to have success with their Carry On movies. The humour was in no way as bawdy as even the early Carry Ons, as it was plain to see The Duke Wore Jeans was pitched to be as innocuous and family friendly as possible, after all, Steele was happier as that kind of entertainer than as some kind of British Elvis Presley.
Better leave that sort of thing to Cliff Richard and get on with belting out those tunes, none of which were exactly rockin' apart from Hair Down Hoe Down which sounded a lot more like the faux-American melodies that Steele had made his name with. Mostly there was nothing too spiky or alarming here, with the plot more concerned with being a vehicle for the soundtrack album while oddly putting across a message of bringing the upper and the working classes together. In a notoriously class-conscious country like The United Kingdom, maybe we shouldn't be to surprised at this choice of material.
What happens is that Tony is wondering what he can do to fend off the plans his parents have for him when he and his manservant Cooper (the ever-reliable Michael Medwin) spot a chap wandering up the pathway to the mansion house and what do you know? He looks exactly like Tony! Yes, it's the old Prince and the Pauper tale once again, and after getting wrestled to the ground this newcomer, named Tommy funnily enough, is persuaded to take the trip to Ritalla under the guiise of Tony. What could possibly go wrong? Not a lot as it turns out, as the cheeky Cockney is charm personified and wins over everyone he meets on the excursion.
Everyone except the princess, that is, who refuses to meet him and is dead set against any arranged marriage. This point is sustained to the extent of keeping Tommy and June apart for the whole of the first two thirds of the movie, so much so that the inevitable romance that blossoms between them comes across as almost an afterthought. In the meantime, we get the stormclouds on the horizon when political intrigue raises its head and it turns out the Prime Minister Basta - sorry, Bastini (Eric Pohlmann) is scheming to force the King (Alan Wheatley) to abdicate seeing as how his daughter refuses to marry. After that a military coup is in the offing, but how seriously can we take that when you're more likely to be musing on what the swing Tommy and the Princess are on is attached to. It all ends happily, with the toffs brought down to earth by means of a Cockney knees-up, leaving you entertained if not exactly challenged.