Some locos unique within their class
Class 20
20084 was the only class 20 to have additional fuel tanks under British Rail ownership (although the class 20/3s have the same modification)
20143 was the only class 20 to be cut up after being sold for preservation (20142 was subsequently accepted by the purchasers when the mistake was realised)
20313 had three different TOPS numbers (renumbered 20194 from D8194 in 1974, it was briefly renumbered 20307 in 1986 but reverted back to 20194 within a few months. It became 20313 when acquired by DRS in 1998).
Class 25
25322 had yellow cabsides, and the only member of the class to work on the main line in the 1990s
Class 27
27043 has neither been preserved nor cut up, having been buried in a landfill site for the past 30 years
Class 31
D5578 had 'Electric Blue' livery
D5579 had Golden Ochre livery (although D5830 has this livery in preservation)
31116 had 'Infrastructure' yellow livery
31215 had a headcode box at one end only
Class 37
37017 holds the record as most northerly travelled item of rolling stock on British Rail when it went through the bufferstops at Thurso station (in 1984)
37093 had 'Police' livery (for a TV advert in 1985)
37265 was the only member of the class to be allocated to Aberdeen Ferryhill (in 1982)
37292 was briefly uprated to 2000 h.p.
Class 40
40127 had both discs and a split headcode at one end
40191 was allocated to the Western Region in 1977
Clarification sought on this one - D255 / 40055 was the only class 40 to be fitted with ETH (albeit only briefly)
Class 47
47046/47601/47901 - the only member of the class to have three different types of power unit, being a prototype for both class 56 and class 58
Class 50
50007 was repainted into GWR green
50149 had CP7 bogies
Class 56
56001 was the only member of the class never to be allocated to Toton
56042 had CP1 bogies
56135 was delivered new in Railfreight livery
Class 58
58014 was the only member of the class to be allocated to Reading (in 1984)
58017 never worked a railtour
58050 had SEPEX traction motors
Class 60
60016 was the only class 60 to be renumbered (to 60500)
Class 86
86501 (the one renumbered from 86608, not th one renumbered from 86258) i the only re-geared Freightliner class 86)
Class 87
87101 was the only class 87 with Thyristor control