I just needed a screwdriver, slip-joint pliers, an adjustable spanner and a cloth.
From the guardian.co.uk
Some magic involving adjustable spanner, an oily rag and WD40 seemed to do the trick.
From the independent.co.uk
And be aware that the danger zone from a large thrown adjustable spanner is about 50 feet.
From the thisisbristol.co.uk
In most cases this will reveal a half-moon-section brass spindle sticking out of the top of the valve, which can be turned using a small adjustable spanner.