THreaded pegs work well unless you come across a large stone underground then they are about as much use as a chocolate fireguard. I tried an impact dril and it made no difference, I also tried carrying a long masonary bit and using the hammer effect and this does work eventually. I now try the drill and if it works then fine, if it doesn't work I resort to using my friendly persuader and find that a gentle ( not ) tap with a 3lb lump hammer usually sorts things out.
------------- Bill
For a licence dated 1997 or later you must add together the plated max weight of the caravan and trailer, if the total is 3500 or less you can tow it. You may even tow a caravan with a MAM greater than the cars unladen mass the restriction was removed in 2013
Perhaps it's just the type I bought, but I'm not really a fan of the srew in peg. I find a rock peg and a lump hammer is quicker and just as effective. I know there are many who like them though.