Alright a bit OT!! but my ditzy daughter for some unknown reason went
and dumped around a litre of Antifreeze down the oil filler of her
Mondeo earlier.

Antifreeze and oil go together about as well as women and cars.......

Fortunately she realised her mistake and some muggins
looks like having to do an Oil change tomorrow;(.

Do an oil and filter change, let her run it for a day or so, then change it
again, just to get rid of any dregs that may be left in there.

If she had run the engine would this have harmed it at all?.

Probably not immediately, but it certainly wouldn't have lubricated all the
bits it should have.

Never heard of anyone doing this before always a first time I suppose!

Try working in a garage for a while, you will see plenty of it!!

Expansion tank full of oil, and the engine run, buggered up all the hoses.

Some muppet who mistook the oil filler for the fuel filler (I kid you not)
and filled (yes, completely filled to the brim!) the engine sump with
diesel. Bloody big bang when he started the engine, and blew a hole in the
side of the block.