- Be present in the room when something vaguely embarrasing is showing on TV. Think love scenes in movies, overly fruity language, etc. They'll sit there watching every last detail while you cringe on the sofa, holding a cushion in front of your face.
- Get given names like Edith, Maud or Nelly. Or, for that matter, Charlie, Alf or Sid. There are as yet no grandparents called River or Chardonnay.
- Use strange and arcane forms of language. Katie's grandmother was going on about a 'weskit' for some considerable time before we realised she was referring to a waistcoat. What time is it, nan? "Ooh, it's coming up to five-and-twenty to seven."
- Remain completely unfazed by their grandchildren's attempts to follow fashion. The most extreme reaction you'll get might be: "That's an interesting hairstyle, dear." Remember - these people faced down Hitler; they're not going to be in the slightest bit bothered by an ironic post-modern mullet.
- Loudly remind your parents, when they're about to deliver a telling-off to you, about that time they tipped over a full potty forty-odd years ago and ruined the carpet in the sitting-room.
- Surprise you when you least expect it. Imagine your grandmother, well north of 80 years-old, announcing that she's formed a modest liking for vodka. Maybe not to any excessive degree - we're not talking about a superannuated Amy Winehouse - but still a little unexpected coming from someone who'd previously been happy with a snifter of Harvey's Bristol Cream after Christmas dinner.
- Pickle. Apparently when you become a grandparent you're given instructions on how to gather various foodstuffs, soak them in vinegar and put the end results in cleaned-out Nescafe jars. Oh, you say, you've seen non-grandparents doing this? That may be the case:
But would they knit a jaunty little hat for the jar?