get yourself a Topeak Mini 18 it has a chain breaker tool, keep it in your kit bag and you just take a link out and ride home.
If you want the good news, if your chain broke, its probably worn and you need a new cassette too
I have a chain tool at home, so popped a link out and stuck it back on.
I suppose I'll have to do some boring loops close by, to check it .
To be honest , I have become a regular mtb'er (prefer openwater swimming to the pool, hence swimming has been less regular than it would be usually), but I would call myself "reluctant", as opposed to "keen".
That said, I am coveting a new bike, front susser, 1 x 12, something light and simple, and less than a k.