Simon Calder has cleared up Ryanair's baggage rules after a passenger says she was charged £50 to bring a water bottle that she had strapped across her body onboard after the airline claimed she was violating its policy.

Ruby Flanagan flew from Dublin to Stansted on 4 February when she was stopped at the gate before boarding her flight back to London, she wrote in the Mirror.

A member of the gate staff pointed to her 750ml water bottle, hanging by a strap across her body, and told her that it would have to go into the bag — and they then told her that her bag was too big and she would have to “pay to get on the flight”, Ms Flanagan said.

So how did this happen? Simon Calder explains all.