You have to remember that there were oftern periods where subclasses would go the entire period without failing once. 421/8's were the very last to do so just two months before South West Trains withdrew them.
357's are the only class which came close to knocking the old 400's off the top and thats becuase they pop between Shoebury and Fenchurch Street all day long. 400's were forever splitting and joining giving plenty of opportunity for calimity and plenty of 5 minute delays but that rarely happened.
Chris Green, then head of NSE, went of record saying that EPB's (which dated from 1951 and were finally killed off in 1995) were "only" achieveing 20,000 between failures after years of neglect yet the Networkers which replaced them have never so much as touched 20,000 with all the care and attention going. Nuff said
If anyone would like to see more MPC stats Roger Ford has compiled a list of Informed Sources articles on his
website - from 2004 all the 'January' articles have a section dedicated to the MPC figures (or MP5MD as he calls it these days). The latest MP5MD article is not yet available there but if you have a January 2008 copy of Modern Railways you'll find it there.
Here are some titbits from the latest
[2007/08] MP5MD analysis:
Seven sub-class groups achieved a P7 Moving Annual Average figure of 30,000+ (of which 6 are 'post-privatisation')
Sub-class -
P7 MAA (
P7 actual)
Silverlink 321 - 49,244 (80,734)
c2c 357 - 45,459 (40,521)
Gatwick Express 460 - 40,688 (115,317)
One 360 - 35,379 (64,483)
South West Trains 444 - 33,908 (28,654)
Southeastern 375/(8,9) - 32,579 (32,870)
Southern 377/3 - 30,004 (28,522)
All the 'Intercity' sets improved from the previous year with P7 MAA figures of 8,000+, and the MML HST P7 actual figure (17,790) was bettered only by the GNER IC225s (19,619).
There is no denying the legendary reliability of the Mk1s (although even they are put to shame by the EMUs of the West Rail (KCR) route in Hong Kong, where the MP
3MD MAA figure was 238,992 in 2006, and no 5+ minute failures occured whatsoever!) but many new(-ish) EMUs are starting to achieve respectable figures in general (not just the 357s, which I believe have not fluctuated that much over the last few years), and Roger Ford is fairly confident that we'll see a fair number of EMUs with P7 MAA figures of 40,000+ next year.