But the monks' lack of accuracy was more than made up for by their enthusiasm for the nature that surrounded them. And who can blame them? As presented in this film, Malmesbury looks so unspoilt that the approach of a Mini to the market cross seems almost sacrilegious.
The highlight of the film is the ascent to the abbey itself, with Betjeman likening the pilgrims who trekked there in the middle ages to modern day holidaymakers flying to the Costa Brava. The abbey featured such tourist attractions as a fragment of the True Cross, and I'd like to think there was a souvenir shop selling holy stuffed donkeys.
Before we go there's time for the story of Malmesbury monk Brother Elmer and his attempt at flying. Less like Icarus than a premonition of the Bognor Birdman competition, he ended up with two broken legs. His commemoration in stained glass is a fine example of the British love of failures.
Talk of aviation problems brings us seamlessly to tonight's instalment of The Plane Makers.
The problems here are being caused by test pilot Simon Wanleigh (Bernard Brown), whose apparent distraction during a flight with Captain Henry Forbes nearly leads to disaster.
After the flight, Simon meets his friend and fellow pilot Terry (Brian McDermott), and both behave rather strangely. While Terry's back's turned Simon swaps their gloves, and Terry acts rather cagey when asked what he was up to the previous Thursday.
As we ponder on this, Forbes is being put under pressure by Arthur Sugden to reveal who was responsible for the mishap in the test flight. The story's made the press, and when John Wilder gets back from his latest business trip both Sugden and Forbes' heads will be on the chopping block unless they can satisfactorily explain. Forbes' instinctive loyalty to his fellow airmen is shaken by Sugden's insistence that this is simply not how things work in the world of business.
The business with the gloves is explained when Simon returns home to his wife Anne (Judi Dench lookalike Zena Walker). A couple of days ago he'd picked up his gloves, only to realise they weren't his. Investigation of Terry's pockets that day revealed that his friend had taken his pair by accident. But he's not aware of Terry visiting recently...
"Do you know why I've been so cool this weekend?" Simon asks. "Because I was afraid to touch you in case I killed you." Anne admits she and Terry have had a fling but insists it's all over now, and she never felt anything other than pity for him.
On Simon's next flight, we learn that there's something wrong with his vision.
At the end of his tether with Simon's errors, Forbes warns him that unless he pulls himself together his career at Scott Furlong's finished. Visiting an optician, Simon learns that the shock of Anne's infidelity has led to a blood vessel bursting in his left eye and causing it to lose virtually all its sight. Obviously this is not the best of news for a pilot.
The Best of Friends is a middling Plane Makers episode, but there are a couple of especially good scenes. When Terry goes to Forbes to explain what's distressing Simon, the chief pilot despairs at the way his men have come to rely on him in times of crisis: "Skipper is not another word for Dad." Reiterating Sugden's dictum that he can't let his loyalty to his men get the better of him, he refuses to hear about Simon's problems, knowing he'd make possibly dangerous allowances due to them.
There's an especially affecting scene where Simon, who cares more about his wife and friend not feeling bad about what they did than what their affair's doing to him, pitifully attempts to convince Anne that he slept with someone else once too. She doesn't believe it for an instant. It turns out there really was a girl he liked, but Terry got her too.
Simon plans to take one last flight, to Rome, where he'll have his eye operated on and then return to Anne with her none the wiser about his sight - he doesn't want her to blame herself for it. But before take-off he's forced to tell Forbes about his blindness, begging to be allowed to go to Rome all the same.
Forbes - horrified at the lengths Simon intends to go to in order to save the feelings of people who've betrayed him - refuses point blank. The episode ends with the painfully buttoned-up Simon thrown off the plane, and preparing to open up to his wife for the very first time.