Royal wedding watchers will be the "eyes and ears" to report any suspicious activity to police on the big day, the officer in charge of the transport security plan has said.

Armed officers will be on patrol as part of an enhanced police presence on May 19, when crowds are expected to travel to Windsor to see Prince Harry marry Meghan Markle.

British Transport Police (BTP) chief superintendent John Conaghan said it is expected a significant number of people will travel by train.

Mr Conaghan, speaking at Waterloo railway station in London on Friday, said people should be reassured rather than alarmed by the increased number of officers on the transport network.

He said: "We want to reassure the public that we have a comprehensive security operation in place, for those people who are travelling through the rail network to the event."

The officer said he hoped the increased visibility of officers would act as a deterrent to anyone wishing to cause harm at the event.

He added: "Wherever they (the public) are on the system they are likely to see police officers, both armed and unarmed officers. We'd ask them not to be alarmed at this."

Mr Conaghan, said terrorism is "certainly something that's at the forefront of our thinking" and appealed to the public to be on the look-out for suspicious behaviour.

He said: "As with any large event we are concerned about a whole range of vulnerabilities and we'd be asking any members of the public and anyone travelling on the system to report to us anything that they considered to be suspicious.

"The public are the eyes and ears and there are hundreds of thousands of pairs of eyes and ears for this event, so there are far more of those out there than there are police officers so it's absolutely essential that they do remain alert and that they do report anything suspicious to us."

BTP is working closely with Thames Valley Police to support the wider police operation, Mr Conaghan added.