Modern diesel have a "DPF" fitted into the exhaust system.

DPF stand for diesel particulate filter.

A very fine mesh which can and does become blocked with what amounts to soot.

And you kind of driving cycle is going to clog the DPF.

My advice would have been don't buy a diesel but as this is too late then it's going to have to be really driven and driven hard to get everything to the right temperature for the DPF to regenerate.

If I recall the renault Traffic cycle was drive at 4000 rpm for 60 miles so the regen would happen.

So I guess your answer is loan it to some teenager once a month to thrash it!!

Is that really true: Yes

Can I do anything … to mitigate the impact: No, IMO

Are you a gambler? Don’t bet more than you can afford to lose. A petrol powered vehicle is less likely to give problems under this type of usage cycle. However, this type of usage cycle would be regarded as SEVERE USE. I would suggest you consider having an engine preheater fitted. Simple models for DIY fit can be had from £100.

Obviously I don't know your situation so please don't take this as any kind of criticism, but do you really need to use a car for journeys of a mile or less (which, as has been pointed out, would be severe use even for a petrol engine)? Is there any way to cut out at least some of them? Just a thought, since I know from my own experience that one can get 'stuck in a rut' of thinking a particular way about how to organize the day.