The first thing I always do whenever there’s any reason to remove battery clamps is to slowly pour a jug of lukewarm water over them. Lead and copper salts from the battery posts and the brass terminals are highly soluble. Half the time this warm bath is all that’s needed to loosen the clamps, though applying a little penetrating oil before you pick up your spanner might also help. Don’t be surprised if the nut or bolt has corroded significantly from its original size.

Avoid the use of vice-grip pliers until you’re desperate: the brass nuts are very soft and will distort and get even harder to remove if you squeeze them. A ring spanner is better than an open-end spanner, and a six-point socket is better than a 12-point. The best tool to use would be a flare-nut spanner, which grips all six points of the nut or bolt head.

Caution is necessary. The battery post is dead-soft lead and not too difficult to shear off completely if you ham-fist the clamp. I’ve been forced to resort to using a cutoff wheel on a Dremel tool to sever a bolt without damaging the post. Don’t forget to use brass – preferably lead-plated – hardware to put it back together. Zincor cad-plated steel will rapidly corrode to the point of failure. You can get the appropriate lead-plated bolts and nuts at the spare parts store.