On Wed, 10 Jan 2007 23:30:01 +0000, The Medway Handyman wrote:

I do carry several box spanners in the 'plumbing kit'. A set for doing
up the nuts when fixing monoblock taps and one that fits 1/2" & 3/4"
backnuts - useful when they are stuck firm, although you have to remove
the pipework first.

Spot on that man. And if you have 2 you can stick the bath one over the
spout of a basin tap to hold it steady while you use the basin-size one to
undo the backnut!