Christian, thanks very much for that explanation. The 1.44 ohms figure
has jogged my memory - last year an engineer came to fix my washing
machine and he carried out a test on the circuit. He told me that the
desired figure for a sucessful test was 1.44 ohms but the figure he got
from my circuit was 3-point-something (I have a note of it at home). he
told me not to worry because some old houses have values above 30 ohms!
So it looks like that circuit is already dangerous and I need a rewire.

Make sure the sockets are RCD protected. Although the circuit still won't be
up to scratch and would still fail an inspection, this removes the main
potential danger.

Christian.