David Splett typed:
"Richard J." wrote in message
news
*In* the Thames?? Do you mean near the Thames, e.g. on the
riverbank?

Being something of a perfectionist I most certainly meant "In"!

I should have realised that! But to me it had seemed unlikely that they
would go to the trouble and risk of digging shafts in the river bed
rather than sink them on the adjacent dry land. Did they decide to do
the former (a) because they couldn't dig the tunnels unless they had
shafts less than x yds apart (where x is shorter than the width of the
river), or (b) because they couldn't gain access to suitable shaft sites
on land?

--
Richard J.
(to e-mail me, swap uk and yon in address)