For the record.

Sometime last week the "Wildlife Pond" group had shots of frozen ponds; Bro. tells me he, at 4-5 miles distant and 4-500' higher has already had frost.
This is the first time I've seen frost here and seen "The Shed end" register a whole -1˚C.
It beat Mrs. Black who hopped in my direction when I rounded the corner.
"Wait a minute, I'll fetch some."
By the time I got a handful of Calciworms and back to the door she'd advanced almost to the door.  GOOD memory, not seen her, to feed for months.
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Came back for two reasons:-
1. Thanks to all for congratulations; I'm not a great fan of answering each individually, for two reasons:-
1. A) The inescapable fact I'm an idle old sine.
1. B) All it, basically does, for me, is cheat by doubling the apparent number of comments.
2. To note that a mere 1˚C of frost was enough to see off the Oca tops. 
BUT:-

"Do not harvest the underground tubers until the last remnants of foliage has become frosted and died off from late November and into December. The longer you can leave the tubers in the soil the better."


"But remember the tubers can double in size during the last six weeks in the ground and don't dig them up till the tops have really died back."
QUESTION - How do you know it's the "last six weeks"?  That's a bit like instructions I once heard:-
"Turn left at the last set of traffic lights." 
WHAT?!?!?