Class 717 - white snout?!

[Magdalia]

To add to previous reply complete yellow “fronts“ were never actually required, only relatively small panels

That's not correct.

When BR corporate blue with full yellow ends was first rolled out in 1966 there was a BRB decision to have full yellow ends on green locomotives too without waiting until they got the full application of corporate blue livery.

I think this must have been relaxed some time in the 1980s, possibly coinciding with fitting of headlights.

 

[swt_passenger]

That's not correct.

When BR corporate blue with full yellow ends was first rolled out in 1966 there was a BRB decision to have full yellow ends on green locomotives too without waiting until they got the full application of corporate blue livery.

I think this must have been relaxed some time in the 1980s, possibly coinciding with fitting of headlights.

Well yes, and I was also thinking more of the situation at about the time the rules changed in 2015, rather than the period headlights were something of an afterthought…

 

[bluegoblin7]

No London Underground stock has (and never has had) yellow fronts, nor the Sheffield Class 399 tram-trains, both of which operate on NR metals.

In addition to the aforementioned engineering vehicles (including the Schöma locomotives and tamping machines in addition to the battery locomotives) the erstwhile Asset Inspection Train also had yellow ends.

 

[Silver Cobra]

TPE's class 68s and the Mk5 driving trailers don't have yellow on them either.