Hi Laurier, Yes up to 4 para vanes would be towed, don't know which type they had some blew up on contact with mines and others cut the mooring cable on submerged mines, then they would blow them up with rifle fire. HMS Roberts hit two mines in her life and survived. Her half sister ship HMS Abercrombie, spent most of her time in dry dock after hitting mines. One time she came out of dry dock in Malta and hit more mines straight away. But it does demonstrate how effective that triple compartment armour belt was.
Incidentally, I came across Douglas Reeman's website and it mentioned that the original cover illustration of his book HMS Saracen was based on a photo of HMS Roberts when she was anchored at Devonport waiting to go to the breakers yard. Cheers Derek