The repair
The expert will say multiple times how difficult it is, how priviledged they are to be allowed to work on it, and so on.
At the start, they ask what the item is, how it got to such a state, what the customer wants and so on. They often remark that they are not sure what they will do to fix it. Very often they remark to the camera just how silled they have been to do something.
We’re never convinced of this, but understand it’s for the show. When the producers are choosing items, a good sob story will be highest priority, then an interesting object, then an assessment of the chance of success (after all, failure is not good tv) and the expert must be involved. They must know what is coming, to have the right tools and so on.
In a sixty minute show you may see five minutes of each actual repair. There may be four in an hour show. Vast amounts of time are given over to the sob stories, clips of other repairs not in the show, scenes of the countryside and of the experts having a chat or a cuppa. All very lovely, but filler.
The impression given by the show is that the expert does it themselves, in the barn. As we said before, there’s no indication of how long any job may take. It could easily be taken away, worked on and then brought back.

Someone remarked to us once that they believed at least some of the experts have assistants and off screen helpers. We don’t know if that’s true, but it doesn’t invalidate the repair. It’s just not usually mentioned in the show.