Tour bus drivers specifically warn passengers travelling on open-top double-deckers not to stand up, according to the director of a sightseeing company.

“The passengers are warned not to stand up on the bus and this is done by having visible signs on the bus and also by the drivers themselves,” Kevin Vella, of City Sightseeing Malta, said.

The company gives out brochures that clearly state: “Patrons are requested to remain seated at all times while the open-top double-decker bus is in motion.”

On Sunday afternoon, a 66-year-old Briton was grievously injured when he stood up on one of the company’s buses as it passed under a pedestrian footbridge in Bay Street.

He hit his head and fell back on to the bus, also breaking his leg.

Mr Vella said the client “accidentally stood up” when it passed under the glass and steel bridge, which had a sign marking a four-metre height limit.

“We are not aware of the reason why the man stood up at that stage,” he said.

Double-decker buses belonging to City Sightseeing Malta did not pass through that road as part of a route but to drop off their clients.

Mr Vella said the company was taking the matter “very seriously”. While it “wishes the injured person a good recovery, it also denies any liability for the incident,” he added.

Several retailers in the area pointed out to Times of Malta that double-decker buses barely passed under the bridge and trucks and lorries had become stuck before.