Getting to the root of the problem

I've tried the special stones in the drinking water, the tomato ketchup in the food, and rushing out to pour water where Nelly, my spaniel, has peed. Nothing seems to work.
It got so bad that the grass died away altogether, so I temporarily fenced off the lawn - Nelly can't get onto it at all - with the aim of reseeding it, even though this seems to be futile because once she gets back on to the newly-grown grass the patches will appear again.
Just recently, though, a thought came to me while walking her in the little park opposite our house that it might all be due to the type of grass. One day I noticed that the grass in our park, which is regularly mown and kept short like a lawn, has not a single brown patch on it, despite the fact that Nelly pees there almost every day, as do lots of other female dogs?
I then noticed too that in our other walking area, Wimbledon Common, no brown patches are to be seen.
I can't think why this hadn't occurred to me before but then, surely, if it was as simple as that, grass seed companies would have cottoned on to it and be making millions out of selling dog-urine-proof grass, as this does seem to be a universal problem for people with female dogs and everybody wants a green lawn. It would be a huge market. But if it's not the type of grass, why are there no brown patches in parks? Has anyone got any clues?
A dog walking friend has just told me that she believes the grass used in council parks - when they sow it from scratch - is different to the usual grass sold in garden centres and is more of a heavy-duty type. Bearing this in mind, I went to a garden centre and bought one that was described on the packet as being tough and containing "fescue" grass and have reseeded the bare patches with it. I'm not holding out much hope, but fingers crossed.
Just out of interest, I'm contacting our council parks department, hoping that they will tell me which grass seed they use.
I did hear that clover is not affected by dog urine because of its deep roots, so if my new seeds don't do the trick, and the council can't suggest anything different, I could try and track down some clover seeds, although that might be difficult.
Failing that, we will replace our dear little lawn with bricks.
Will let you know how we get on and if anyone has any better ideas, apart from those I've tried, do say.
Julia Lewis, by email