Make sure your cabin bag measures up to the rules

If you've taken a flight recently then you may have noticed a bit of a kerfuffle at the boarding gates.

- Martyn James

While waiting to board a flight to Spain, I heard a very well-spoken lady using some very unladylike language as she argued with a member of the airline staff (note: never, ever do this). Over at another gate I watched a family burst into tears as they nearly missed their flight over a technicality. Meanwhile me and my fellow travellers all desperately tried to squish our cabin bags in to what the industry calls 'baggage sizers' - the metal luggage prisons that airlines use to check our bags are not oversized.

The luggage wars are well and truly under way.

It's recently been reported that Ryanair has been paying bonuses to staff for every oversize cabin bag they spot - and are considering increasing this incentive. Meanwhile, other airlines are allegedly paying £1.20 to airline staff who do the same.

So why this sudden crackdown on passengers and their carry-on luggage? And what are the rules?