Rivals or partners?

Two steam loco designs built by rival railway companies before Nationalisation team up to double-head a heavy charter train through the Pennines. Here ex-LNER Class B1 and ex-LMS Class 5 wait to leave Carlisle Citadel Station on a very wet and cold January day in 2014 to tackle the stiff gradients of the Settle and Carlisle Railway.
I was prompted to post this following Pete Weber's recent posting of a photo showing two Class 5s double heading the Tin Bath special at Sheffield.
The Class 5s and the B1s were widely regarded as the best examples of middle power range 4-6-0s built in Britain in the late steam era. The 'train engine' in this shot, Class 5 no. 45407 also featured in Pete's picture. The 'pilot' here is B1 61264.
K30+DA*16-50mm lens