Wisteria is huge and next to my gas supply pipe.

[Swerving]

I may well have given it the death sentence by recently cutting it well back.

It always flowers twice a year and is very healthy. It spreads above and below one window and above another then over a doorway - so it is long.

The trunk is now quite large and seems to be affecting the gas supply pipe in that the outer casing (plastic) is now distorted. I wanted to get close to see if I can smell gas - no smell as yet.

I was wondering what are the roots like. Are there lots and spread out or deep ones going down. Will I have to remove it before it does any serious damage?

Wisteria have been planted against house walls for hundreds of years so I wouldn't worry about the roots but you might want to get the gas pipe checked out. And this isn't the right time of year to prune them strictly speaking but you're unlikely to have killed it. You might not get very many flowers though. You can cut wisteria back very hard but you're supposed to do it in Jan/Feb then again in July/August

Thanks ChristinedePizan, that makes me feel a little better. Will keep my fingers crossed for it to survive the shock.