This is perhaps a stupid question but here goes...

I bought some new anti roll bar links but I'm unsure of how to fit them. The previous style that I removed had a hex in the end which made it easy to hold whilst tightening the nut. The new ones have nothing on the end but do have a flat on the joint that can be held with a 16mm spanner. Once it starts getting tightened the spanner ends up jammed between the ball joint and the bracket. The only thing I can think is a thinner spanner?

Yup, thinner spanner (or attack the one you have with a grinder).

I used a bit of plate steel I had lying around and cut a slot in it with a grinder.

Use a cycle cone spanner.

Make sure the thread is clean and use something to stop corrosion or galling so you can get them out if you ever need to. Thinned down, or plate spanners aren't very strong. Don't want to have to resort to making extra long jaws with provision for a keeper across the end so they don't spread. I usually use the weakest form of loctite for that sort of thing.

If you are thinning a spanner start with a decent one. Last time I tried that with a "don't know where it came from cheapy" out of the bottom of the toolbox it turned out to have a crack inside the jaw forging. So I made a plate one.

Usually the simple approach works just fine but sometimes the Head Gremlin turns up with a full squad and, metaphorically, says "hold my beer!".

Clive

Taking them off isn't a problem with an angle grinder and 1mm cutting blade. You just slice lengthways so the two halves of the nut fall off.

Thanks for the suggestions. I found that I had the perfect tool. I forget what it's for (some garden equipment I think).