Sunday night’s superbly made episode of ITV’s Morse spin-off, Endeavour, was much concerned with a visit to an Oxford missile factory by Princess Margaret. As catering arrangements were discussed in the opening moments, the word ‘refreshments’ was accompanied by beguiling scenes of lots of champagne glasses being lavishly filled.

Not for HRH! The programme went out days after we learned — from archive material relating to a royal visit to Mauritius — that Yvonne (as Private Eye always called her) usually specified wine without bubbles.

She also famously liked her whisky. I vividly recall a visit the princess made to Oxford in connection with the Bodleian Library appeal. “Where will she be sitting?” I asked as we entered the Divinity Schools for dinner. “That’s pretty obvious, isn’t it?” one of the organisers replied, directing my gaze to a centrally positioned table on which stood, very prominently, a bottle of the Famous Grouse.

Sunday’s Endeavour featured some fine acting, including that of Jenny Seagrove as a rich bitch with a big family stake in the armaments business.

I wonder if anyone else noticed one very minor slip in her presentation of this top-drawer lady. She pronounced ‘envelope’ with the first syllable given the French ‘on’ sound, in the way no real toff would do.

By an odd coincidence the Duchess of Cambridge was in trouble with the same two letters in an appeal video broadcast in a news bulletin straight after Endeavour.

“We can insure . . .” she said — when ‘ensure’ was what she meant.