The male and female bushes are brass but the lock nuts and plate are steel. Phil D spotted it first and took the photograph. The singles are connected direct to the 300A busbars.
I’ve worked on English Electric CFS switchgear for years and I like the stuff. I’ve cobbled various types of switch fuse units on to EE busbar chambers a few times but I’d be ashamed of that effort. Still what do you expect from Network Rail contractors?