As Jack Camplin pointed iut "Most cat shelters in the UK will not release a healthy cat to a home where it will be kept inside all the time." I know the cat sanctuary that let us have these kittens would never have let anyone have them who didn't intend to allow them out.

We go out with them on a leash sometimes, while they are too young to be allowed to go out on their own. The thing with cats is, you don't take them for a walk, they take you, and you follow. It's rather like Les Barker's "Guide Cats for the Blind" -

"This master/servant things o.k. but not that way around
We don't do the 'faithful' subject, we don't do the daily grind

My guru always said's approach reminds me of the way my wife dealt with our last cat when he was young - she'd carry him out by the forbidden hedge while the traffic went past and growl at him. It seemed to work all right - at least he never went out that way so far as we know.