Next time you're walking along the pavement and a car goes past, have a think about the last time one stopped. Maybe I just have the face of someone who knows his area, but it used to be every day that I was asked for directions by a driver.

But not any more. The last time for me was back in the summer when a family trying to find a local business were confused by the one-way system.

They clutched a printout from Google Maps as if to show they weren't totally directionless loons but had planned ahead. I was startled by their request, so infrequently does it happen now.

And that is the difference in 2009. Five, 10 or 100 years ago, people would set off to a place they'd never been before with a quick glance at a map and the cheery knowledge that they could ask passers-by nearer their goal.

One thing has ended this friendly reliance on other people, and it's not the wrongly hyped fear of strangers. It's Google Maps, sat-navs and the computerised mapping of every inch of our land from miles above.

Now they're photographing it from a van, too. They're everywhere, they can see everything. But here's a salutary tale to burst their bubble, and it starts with that great British institution, the Duke of Edinburgh.

For it took the duke to dampen Google Maps' proud boasts about being cutting-edge. He revealed the maps are as up to date as a Jimmy Tarbuck routine.

Let me explain. The duke and his missus visited Google last year and the bods there proudly showed him Buckingham Palace on Google Maps. Then he asked to see the building that they were standing in, Google's headquarters in north-west London.

Only, instead of the Google headquarters, the picture showed a building site.

Cue embarrassed faces: when the picture was taken, the building was still being constructed.

Perhaps the duke was under the illusion that Google Maps shows the world as it is the day you look at it. Sorry yer 'ighness, you're not even close. The one of London is at least three years out of date – I know, because it shows my beloved Highbury with Arsenal's new stadium across the road still being built.

So I decided to carry out a bit of in-depth research. Just how long ago was the picture of my house taken? Could I work it out? It was, after all, taken from space.

For half an hour, I admit, I became obsessed with this nerdy project, but it was a magical bit of detective work. So, here goes.

I live in Malmesbury – a lovely place in north Wiltshire. And the first thing I spotted was that the historic abbey was in the picture. Phew. So this picture was taken at some point after 1180AD.

But I instantly knew it wasn't exactly up to date. The A350 Semington bypass, which was built a couple of years ago, was just a line drawn on the map, over the top of a picture showing lovely fields. Google's image of Malmesbury, and indeed most of Wiltshire, was blurry – you couldn't zoom in close enough to see anything other than green fields, brown developed land and maybe roads.

But then, just recently, a new picture replaced the old one – it was much more detailed and crisper. It was so clear you could see that my house, built in 1971, was there. The detail was so good you could just about make out my late father-in-law enjoying the sunshine in his usual spot in the back garden.

T here was also the housing estate across the river, finished in the late 1980s, and the Dyson factory that shines like a beacon over the town was there. It was finished in the mid-1990s.

Any other clues? The Somerfield car park was full of cars, so the store must have been open, and it had been open a while that day. But Dyson's car park was empty, so it must have been a weekend. Judging by the shadows, it was still mid-morning, and a lovely day, too. But then I spied something odd.

Where was the cul-de-sac next to mine? It was a building site. This was the one built on the abattoir from which the Tamworth Two pigs escaped. That was in 1998 and, the following year, the place closed and homes were built there pretty sharpish. So this picture dated from about 1999.

And then came the biggest clue of all for precision. In the town's main car park, by the river, there were no cars, just a huge funfair.

I was astonished. It comes for just three days a year during the carnival on the first weekend of September, and there it was, captured for ever more. People from all over the world come to Malmesbury to see its abbey, history and naked gardeners. Imagine their disappointment if they base their holiday decision on this map.

You can picture the scene – American dad is planning the tour of Britain and he decides to stop somewhere after doing Stonehenge and Bath. Malmesbury looks nice as he spots the town on Google Maps on his home computer. He then turns to his sceptical children and utters the words: "Look kids, they've got a funfair there, too."

I went further afield for more clues, scouring the satellite image. And I found a clincher six miles away in a field near the village of Dauntsey. Clear as day, the field was full of cars. This was the great Sunday morning car- boot sale in full swing.

So I could, with some accuracy I reckoned, place the time when the image Google used was taken. It was snapped at some time between 10am and 11am on Sunday, September 5, 1999.

So don't worry about an invasion of privacy. And don't base your holidays on Google Maps. It isn't the here and now, it's a snapshot of history.