Two men are said to have climbed the building before getting down and fleeing the scene, police said.

Footage shows a hooded man shuffling along the ridge of the roof, around 60 metres off the ground.

After reaching the mast he hauls down the flag, video shows, before trying to raise the Palestinian flag in its place.

The crowds below celebrated as Israel's flag was thrown to the floor, cheering the man who then climbed down and ran away.

The news came as the home secretary warned waving a Palestinian flag on British streets "may not be legitimate" if it is done to show support for acts of terrorism.

In a letter to chief constables across England and Wales, Suella Braverman urged officers to use the "full force of the law" against shows of support for Hamas following its unprecedented attack against Israel.

It comes after vigils were held in Westminster for Israeli civilians killed and held captive, while pro-Palestinian rallies took place outside the Israeli embassy in Kensington.

Read more: Israel vows to 'wipe out' Hamas - live updates

Ms Braverman said targeting Jewish neighbourhoods, waving pro-Palestinian or pro-Hamas symbols, and chanting anti-Israeli slogans could all amount to public order offences.

Hamas has been proscribed as a terrorist organisation by the UK and many other Western nations, including the EU and the US.

Because of this, she reminded police forces it is a criminal offence for people in the UK to:

• Belong to Hamas or invite support for the group

• Wear clothing in public that suggests they are a member or supporter of Hamas

• Publish images of flags or logos linked to the organisation

"At a time when Hamas terrorists are massacring civilians and taking the most vulnerable (including the elderly, women, and children) hostage, we can all recognise the harrowing effect that displays of their logos and flags can have on communities," Ms Braverman wrote.

She added unrest in the Middle East has previously been used "as a pretext to stir up hatred against British Jews" - and there is an "obvious risk this pattern will be repeated during the current conflict".

"In the past, this has included vandalism of Jewish businesses, desecration of memorials and religious sites, physical and verbal abuse of Jews on the streets, convoys driving through Jewish neighbourhoods hurling antisemitic abuse, and proliferation of antisemitism online," she warned.

Read more:
Babies killed in Hamas attack, Israel says
Why is Hamas in conflict with Israel?
What is life like in the Gaza Strip?

On Monday, a kosher restaurant in Golders Green - an area of north London with a significant Jewish population - had its windows smashed and a cash register stolen, while "Free Palestine" was daubed on a nearby railway bridge.

The graffiti is being investigated as a potential hate crime by the British Transport Police, with local authorities describing it as a "deliberate attempt to intimidate the Jewish community".