I have a BR blue one and it is an excellant runner you wouldnt know it was their and It never derails even on the most foul trackwork
As for some information while they near always ran in pairs in the Blue period I have seen a picture of 2 class 20s running a sprinter replacement service consisting of 2 mk1 Sks and a Bg aswell as the 2 class 20s
As for some information while they near always ran in pairs in the Blue period I have seen a picture of 2 class 20s running a sprinter replacement service consisting of 2 mk1 Sks and a Bg aswell as the 2 class 20s