The Queen has postponed a scheduled visit to Scotland Yard's new headquarters Thursday (23 March) following the lone-man terror attack at Westminster Palace on Wednesday.

The Queen and the Duke of Edinburgh were to have opened the new Metropolitan Police Headquarters at the Victoria Embankment, but Buckingham Palace told the Express.co.uk that the visit will now be rescheduled.

A Buckingham Palace spokesman said: "In light of today's (22 March) events, the decision has been taken to postpone The Queen's engagement to New Scotland Yard tomorrow. The visit will be rearranged for a later date."

The newspaper said that the Queen was in residence at Buckingham Palace when the attack at Westminster took place. Armed police patrolling the palace closed the gates following the attack.

Royal Central said that there are currently no plans for the Queen to leave London although precautionary measures are expected to be put in place.

Three civilians and a 48-year old unarmed police officer Keith Palmer were killed in the attack. The terrorist was later shot by another police officer and died from his injuries.

Police warn public to avoid certain roads

Separately, the Metropolitan Police are asking the public to avoid certain areas in the city to allow emergency services to deal with the ongoing incident.

The police also cautioned public that officers, including firearms officers are still at the scene of the attack and "we're treating this as a terrorist incident until we know otherwise."

Londoners have been warned that there will be extra armed and unarmed officers on the streets of London following the terror attack.

Police seek those with images of the attack

Police are also asking members of the public who have photos or video footage of the incident in Westminster to pass them to the force.

Those with relevant footage can upload them here.

Casualty Bureau

Those who are worried about family or friends in relation to the Westminster incident can contact the Casualty Bureau on 0800 056 0944 or 0207 158 0010.

The police also urged those who were involved in the incident and are safe, to update the bureau.

"Demand will be high. Please keep trying. Staff are working hard to speak to as many people as they can." it said in the statement.