As this seems to have happened roughly 20 months ago, lets say 15 months, it's possible that two lots of MOT's have been done since, so DVLA now have records of the car, same with road tax and insurance.
But in the first instance...
When the "Friend" tried to register the car in England with DVLA into said "Friends" name DVLA would have written to the last registered owner to ask that person have you sold your car?, if they didn't answer back within a few weeks it would have been registered into the new keepers name, if the correct owner said NO i never sold it, then NO new registration document would be issued into "Friends" name.
Also the correct legal owner should have notified DVLA of the new owners name and address where ever they lived.
if the old owner hasn't told DVLA of the sale they are still liable for fines, insurance etc, even not telling DVLA they sold it also carries a hefty fine.
To obtain a new tax disc, presuming at some point the "Friend" needed one, the car had to have insurance papers in the same name as on the registration document.
So far the post is by the way of not all being told dubious.
As we all know their is an almost 100% correct way of doing this, finding out who own's / has the car, and doing something about this, but this is where it all falls down, England at the moment is all but totally corrupt when it comes to, for this post cars, so anything and everything can be overridden...If you know how.
I sold 5 cars in a batch a while ago to Eastern Europeans who were going to export them, when they came back to pick them up they asked me for some tape to stick the tax disc's in the screens.....I asked how did you get the tax disc's?...they said same as you, from the Post Office.....I said, okay how did you get the tax disc's....... when i still have all the papers then? oh we have friends in Post Office, they paid double the correct amount, i have no doubt they didn't export them... as i say corrupt.
The "Friend" didn't even have to come back to England to register this car, the local English and Spanish newspapers carry an advertisement from an English chap who "Sorts" out a new registration document, new MOT, new tax disc, everything you would need, and in some cases registered the papers with DVLA, he has just been caught, given next to no sentence or fine.... his knowledge has been passed on to his heirs.