The telephone number of Wendy, my best friend at school was 227.

Ours was 526. In those days I could remember most of my friends’ telephone numbers.

Now, of course, it’s a different story. I can recall a couple of six digit numbers – including my parents’ – which I regularly dial using the old-fashioned museum-piece telephone and landline.

But I can remember only the last three numbers of my sister’s London landline, and I can’t recall any of my friends’ mobile numbers or their land lines, because I normally text them, and don’t need to key in the digits.

Nearly half of people can remember no more than three telephone numbers because they have become so reliant on storing information on mobile phones, a survey has found. They said that if their mobile died, that is all they could remember.

It’s not only phone numbers. People don’t need to remember birthdays or other key dates on the calendar nowadays – the phone will keep a record and alert them. My friend’s phone beeps to let her know when her dental check-ups and MOT is due.

I’ve even seen people in the supermarket checking off lists on their mobiles. While I’m racking my brain trying to remember what I went in for, before I became distracted by a not-to-be-missed deal on Sugar Puffs, smug shoppers are calmly calling up their weekly shop on their iPhones.

Mobile phones are doing for us what we used to do ourselves. We ought to be careful. I’m no scientist, but I would have thought we need to give our memory banks a little test run every now and again. Otherwise, there will come a time when they seize up. We will be out and might remember where we live and will have to ring ‘home’ (we don’t need to know the number) for directions. Of course, if we have a sat-nav we won’t have to remember whether it’s left or right at the Black Swan, because it’s all done for us.

The only time we really give our memory a work out is when our mobile phone goes missing after we’ve switched it off.

We are far too dependent upon mobile phones. No wonder, as the survey found, a quarter of us feel panicked when our battery runs out. As I regularly say to my youngest daughter, it is like a life support machine.

I mourn the days when we all had three-digit telephone numbers and remembering them was as easy as 123. Now the only number with three digits is the emergency services – and they had better not change that to half a dozen number or we will all be in trouble.