In my days at Ruislip Gardens I remember the master cutler train going through on it's way to Sheffield at 6.30pm. Does it still run? Used to watch it on my way to cubs.

Per Wiki: As at November 2019, the Master Cutler name is carried by the 07:25 departure from Sheffield and 17:02 departure from London St Pancras. This is identified by the 'M' in the notes at the top of the timetable for these particular services.

No longer passing through Ruislip though and I suspect no longer a dining train, so only the name lives on.

There is a heritage train with the same name - see link

I used to spot that train, usually West Ruislip because the water troughs there were an added attraction in steam days. The "Master Cutler" Pullman trains no longer exist, nor does the Great Central line to Sheffield and Nottingham on which they ran. The food and service was impeccable, it was all first class with a premium fare and of course its own "Blue Pullman" trains in the diesel era.. The "Master Cutler" name sort of lives on but it's just another East Midlands train. Sometimes there's a trolley service.