HOW is this for a story? A daughter, concerned about her mother’s treatment in a care home in Chile, hires an agency to install a “spy” as a resident. At the same time, a documentary crew, supposedly there to make a film about everyday life in such an establishment, sets out to capture the results.

Undercover OAP: The Mole Agent (BBC4, Monday), turned out to be both tragic and joyous. Sergio Chamy was the 83-year-old 007. The job ad had called for someone competent with technology, but Sergio had trouble distinguishing Facetime from his phone’s camera.

What he had instead, and in abundance, was charm and genuine concern for others. Through the simple but wildly effective method of talking to people, mostly women, he found out what ailed them, and it was nothing to do with medication being missed or ill treatment of any sort.

The residents were suffering from loneliness, waiting for family visits that never came. Though recently widowed and still grieving, Sergio, with his children and grandchildren, could see how lucky he was compared to the others in the home. He couldn’t wait to get back to his old life after his three month stint, but equally he could not forget the people he had met.

Maite Alberdi’s documentary, part of the always excellent Storyville strand, could have gone wrong at so many points. Was it right, for example, to film residents who may not have been able to give informed consent? Was any of it scripted?

Alberdi’s film worked beautifully because it took its lead from the gentlemanly and dignified Sergio. Heroes come in all shapes and ages, indeed. One to catch on iPlayer if you missed it. Oh, and it is up for an Oscar to boot.

Interior Design Masters with Alan Carr (BBC2, Tuesday) has helped to get more than a few of us through the misery of a second lockdown. After seven weeks of amateur designers overhauling everything from hotel bedrooms to offices, shops and beach huts, it was time for the final.

In the pink fluffy corner with leopardskin accents was Siobhan, with architect Lynsey in the swish, quasi-minimalist, Scandi blue corner. As ever there was a lot of design-speak flying around, and the word “genius” had to do some very heavy lifting. The whole series might have been flat and moody and characterless, like an airport hotel, if it was not for Mr Carr.

The bespectacled one brought the fun to an otherwise unremarkable programme. He put the contestants at their ease while just mocking them gently enough to keep the folks at home snickering. No one was made to feel bad, and the finished holiday homes featured in the final were places you would actually like to stay in. None of your Changing Rooms MDF rubbish here. Like Siobhan installing a mural, a third series is inevitable. Hilda Ogden would have loved Siobhan.

Hard to believe that there is only one more episode of Unforgotten (STV, Monday) to go. Where has the time gone? Chris Lang’s drama has managed, as ever, to handle multiple story lines and characters with ease, always keeping in step with viewers. Unlike some other crime dramas we could mention. Take one pace forward Line of Duty (BBC1, Sunday).

The new series began at the usual breakneck pace, with a blizzard of acronyms blowing and plot points coming at the viewer thick and fast. We met with old faces, Ted, Steve, and Kate, and some new ones. Chief among the latter was DCI Joanne Davidson (Kelly Macdonald), an enigmatic copper hunting the killer of a journalist. Not that the description “enigmatic” helps much; in Line of Duty everyone is enigmatic. Even good old Ted, he of the catchphrases fame, turned enigmatic in the last series. If AC-12 has an office goldfish it’s probably enigmatic.

The hour flew by, and then the questions arrived like migrating birds for the summer. Out there in social media land there was much confusion over who was who, what was what, and debate raged over whether DCI Davidson was enigmatic or just a bit boring. A couple of critics got in on the act – like they know anything – even going so far as to wonder if, whisper it, we had maybe hit peak Line of Duty and it was all down hill from here.

Nonsense. Given the success of Jed Mercurio’s police procedural it was perhaps inevitable there should be a backlash at some point. But we are only one episode in. If we didn’t have questions there would be something wrong.

Line of Duty has always walked a tricky path between intriguing and plain old baffling. That is the way fans like it. So what if some of us are tempted to go full Carrie Mathison of Homeland and take over a wall in our home to set out all the clues? Makes a change from a mural. That said, we’ll keep an eye on the situation. Mind how you go, AC-12.