Sorry to hear about your father, MM.
As andyl said – the car forms part of his estate, so should be dealt with as part of that.
That said I know of a couple of families in the same position who just progressed and sold the car on (presumably signing the log book themselves). I think the took the view that moving the car on was more important and if anyone had challenged they would have made sure the estate had the money. In both cases the cars were worth very little. In fact, I think I ended up with one of them….
I suspect there are legalities but there’s also pragmatism in these situations.
Hope the sale is quick. As quick as your RS6..!