Smokeyone wrote:
First of all, I may be mistaken but I am reasonably sure that at one
station I saw a section of track with four of the spring clips missing
in a row from the shoes on the rail. I think shoes is the correct
name. Is this now the norm on the Underground...........

See photo at
http://www.trainweb.org/tubeprune/Tr...ing%20Mark.htm

The term is "chair", not "shoe", and the spring clips are called "keys".

Where exactly did you see this? Did the chairs either side of these four
have the keys inserted?
--
Richard J.
(to e-mail me, swap uk and yon in address)