Whilst not a recommended solution (and these days you Dad could have been done for something, especially given it wasn't even his dog etc) it can work with the right dogs / situation.
We (well Mum) is looking after a stray Lurcher atm and he loves to play (especially with other dogs) but is quite rough (the vet thinks he's only 12-15 months old so that could be part of it). He's about twice the size of daughters terrier but the terrier older (~6) and whilst he will join in and have a play, he doesn't like it when it get's too rough and will tell the lurcher in no uncertain terms when he his. The problem' is that the Lurcher has a short memory and will dive in again a few mins later. ;-(
The Lurcher has a girlfriend over the park who is his size but a bit heavier and so isn't overpowered / intimidated by him and so the play is much more balanced. ;-)
When my stepdaughter (39) died a year ago she left a Cavashon. She would bark on hearing any noise outside and whilst it wasn't that loud (compared to the terrier especially) she had to get at least 5 barks in per noise, no matter what you did to stop her (stubborn little moo). Even if you gently held her muzzle shut after the first one, you would still get the muffled noses, till she had done all 5. ;-)
After a good few months we came across (by complete chance) a couple who were had been looking for a dog (specifically a Cavashon) for some months and long / short (after several house visits, group dog walks and her staying with them for a couple of trial days etc) they took her on and she's now very happy in a large bungalow (rather than a flat) with a big back garden. He was happy that their holiday was cancelled as he didn't want to leave the dog (she was coming back to us for a fortnight). She sill does her funny back thing if she hears a noise but they are very happy about that as it's often a warning that there is someone approaching the house or a fox in the back garden. ;-)
Daughters dog knows we have arrived as he recognises the CV joint clicks on out Meriva and lets out a muffled 'woof'. ;-)
Cheers, T i m