Found the one Frenchman with an excellent command of the English language

[Micael]

Behold this French aristocrat giving a (likewise excellent) tour of his castle, and marvel at the fact that there appears to be at least one Frenchman who have managed to achieve a nigh on impeccable grasp of English:
https://youtu.be/pJd9OtmrTKA

There must be a good few years spent at an English boarding school behind that given the casually posh accent, right?

[Zen9]

Quite a few French aristocrats have good command of English.
There was one I met at his chateau outside Cherbourg, around the late 90's. It was end of season and virtually no staff around.
Then out he came from an converted barn.
Charming chap he worked the ticket machine for us and warned us about his wife....
I remember him well, balding, almost English aristocracy in dress (patches of the elbows of a well worn jacket). Slightly downtrodden in demeanor.
He joked with my uncle and frankly could have passed for an Englishman.

The wife stormed out of the building as we walked round the grounds and demanded proof we had tickets. The sort to wear gold shoes, dye her hair blonde and still pretending to be 25 at what must be something like 60. Very aggressive.

[Micael]

Quite a few French aristocrats have good command of English.
There was one I met at his chateau outside Cherbourg, around the late 90's. It was end of season and virtually no staff around.
Then out he came from an converted barn.
Charming chap he worked the ticket machine for us and warned us about his wife....
I remember him well, balding, almost English aristocracy in dress (patches of the elbows of a well worn jacket). Slightly downtrodden in demeanor.
He joked with my uncle and frankly could have passed for an Englishman.

The wife stormed out of the building as we walked round the grounds and demanded proof we had tickets. The sort to wear gold shoes, dye her hair blonde and still pretending to be 25 at what must be something like 60. Very aggressive.

Oh that’s wonderful. Generally aristocrats across Europe were well versed in languages in the past, however my belief is that this is something that has partially went away as financial fortunes (resulting in an inability to pay for governesses and/or exclusive boarding schools) and priorities have changed in many families. This gentleman appears to be an exception to that, and I hope that the following generations will keep it up.

[Straker]

There must be a good few years spent at an English boarding school behind that given the casually posh accent, right?

It's that weird mix of Received Pronunciation and generic home counties that says boarding school or Oxbridge (less likely though most people will not lost an accent at that age without deliberate effort and in that case why not just RP.) Without the video for context I'd think he was a UK native English speaker.

Saw the video a few days ago but seeing this thread I'm now I'm curious what his French accent sounds like to native French speakers.

More generally a 90% of the French people I have worked with have been completely fluent in English with a fairly generic mid-atlantic accent (or in some cases an amusing mix of regional UK accent and regional French one). Perhaps the only things that would catch them out would be the strange mix of idioms/regional dialect that various parts of the UK have. Generally they have chosen to work in a profession where work overseas requires it though.

[Micael]

I’ll wager a guess that he sounds aristocratic when speaking French. It would be quite the contrast — and amusing — if he spoke some low brow dialect in French while speaking posh English.

[Zen9]

Just for giggles.

Afterwards my family figured we'd just met the characters for a new 'Allo 'allo like series.

Charming but downtrodden Count.
Gold digger wife, determined to extract every penny.
All we needed was the ubiquitous French handyman in blue overalls and a flat cap with a portrait of Stalin in his shed.
Maybe humorous entanglements with a French taxman and corrupt local councilor.