As Macbeth so nearly rightly said, a bad travelogue is but a walking shadow; a poor player that struts and frets its hour upon the stage and then is heard no more. It is a tale told by an idiot, full of sound and fury, signifying nothing.

Minus the fury, this is a fair summary of Miriam Margolyes and Alan Cumming’s Caledonian travels – including a trip to Cawdor Castle – in Miriam and Alan: Lost in Scotland (Channel 4), the first in an unaccountable and possibly unconscionable series of three hour-long episodes to follow them trundling round the blameless land in a campervan, “rediscovering” their roots.

Cumming grew up on the Panmure estate, near Carnoustie, on the east coast, where his father was head forester. Margolyes’s Jewish immigrant family settled in Glasgow. One of the duo’s first visits is to Allison Street, where her father lived as part of a family of six in a couple of rooms before going on to become a doctor. In the first of what will become many anticlimactic moments, they get no further than the (clearly new) front door of the building that housed them back in the day. There’s also a cringeworthy moment when, as Margolyes is reminiscing, a Glaswegian man on a mobility scooter stops to chat (he is subtitled for viewers) and neither presenter is quite comfortable with the idea. “We’re having a tender moment!” cries Cumming, a little too snappishly to be funny.

Then it’s on to a tartan mill, where Cumming has commissioned a tartan to commemorate their trip. “Aliam” comprises stripes of turmeric (for the soil of Margolyes’s adopted home, Australia), blue (for Hanukah), lilac (for lesbianism;she is gay – you’ve probably heard), green (for Cumming’s rural childhood), and pink (“a lusty colour and we’re both quite lusty people”) on a yellow (his favourite colour) background. They have some of it made into a toilet seat cover but Margolyes, because this is her shtick, asks “if I can have my shit first?” “I’m all for that,” says Cumming, and withdraws.

Margolyes’s shtick is not quite as relentless as it has been up until now in her late television career renaissance. It is nice for it to take something of a back seat here, when it has begun to seem effortful and wearying for purveyor and viewer alike. Still, there is enough left to satisfy those whose appetite for her humour remains unabated. We learn that her knickers fell off during her first driving test (dearth of elasticity rather than abundance of lustiness), get an “as the actress said to the bishop” in and various play made with hoses (“You want to get your nozzle out”) and roses (“massive hips”) in the garden. Godspeed.

A thread running through the episode is whether Cumming is related to the priapic first baron of Cawdor, for whom many of his female ancestors worked below stairs and to whom he bears an uncanny resemblance. A DNA test is taken by him and Liza Campbell, daughter of the 6th earl. The results are teased to the point of exhaustion before joining the pile of anticlimaxes, alongside the unseen flat and the unseen house in Fordyce bought by Margolyes and Bill Paterson, with whom they walk through the village that they both fell in love with 40 years ago.

A more justifiable – and, in a twisted way, welcome – anticlimax was Cumming’s visit to his old home, where he grew up with an abusive father and which holds nothing but unhappy memories of being neglected, terrorised and traumatised. His quiet, charming gentleness that has brought out the best in Margolyes seems to have brought out the very worst in his father. “He was particularly cruel to me and my brother,” he tells Margolyes matter of factly, as they emerge from the shed in which his father once forcibly shaved his head. “But everyone was scared of him.” They sit in the sun and wait for the shadows to recede. Cumming decides that, although they have permission to go into the house from the current owners, he won’t. He looks around the garden instead. “It would be a lovely place to live if you didn’t have massive childhood trauma in it.”

The rest is filler. If you’re in the mood for the gentlest of travelogues, the slightest of narratives and some nice views, you won’t be disappointed. If you are looking for anything else, you’ll probably be strutting and fretting quite a bit before the hour is done.