What constitutes a sensible level of security? I only ask because I was passing through Heathrow recently and had my shoes scanned. Not once, not twice but three times.

The first time was in a bog standard X-ray scanner, along with my hand luggage and plastic bag of liquids.

Within two seconds of putting my shoes on, I was ushered into the lane for the dedicated shoe scanner. I knew that to say’ But how could I have slipped something into them in the last two seconds’ was pointless – any attempt at remonstration in such surroundings invariably leads to even greater delay.

As I put them back on for the second time, I was hustled by someone from behind, who was tutting at the length of time I was taking to tie my shoelaces. I began to realise just how those hilarious (if you are not a participant) airport rage incidents you see on Airline kick off.

By the time I reached the gate, I was sure that the powers that be would have decided that my shoes did not constitute a security risk. Wrong. I was asked to remove them by the gate security staff – this was a flight to Washington – for them to be scanned a third time.

In the days when cameras used film rather than pixels, X-ray scanners used to have signs that said photographic film is not harmed by repeated passage through these machines. I’m now beginning to wonder whether they should put something up about your footwear. In the meantime, I’m going to start to wear slip-ons.