LMS Stanier Black Five, No.5000 - the cab was open to visitors [as there were enough trained volunteers] which was interesting - I'm more used to narrow-gauge engines.

The headlamp code designates "Royal Train" when the Monarch is aboard. Not quite fully correct, given the vehicles marshalled behind 5000. If you want to be pedantic, it should be "Class A" ie express passenger ...

didcotrailwaycentre.org.uk/article.php/571/going-loco-october-2023

To the right is E5001, a class 71 electric locomotive, that can only operate on the 750v third rail system.