Thousands of school children descended on Westminster today for a second strike demanding the government change its environmental policies.

More than 15,000 youngsters gathered outside the Houses of Parliament to call on politicians to declare a “climate emergency” to deal with the “ecological crisis” threatening the planet.

They marched from Parliament square at midday to the gates of Downing Street, before congregating around Buckingham Palace where they were met with a heavy police presence.

A few of the placards read: “By the time we're in charge it will be too late”, “we want you to panic” and “the greatest threat to the planet is the belief someone else will save it”.

Some of the other students formed a sitting protest on Trafalgar Square and climbed onto Nelson's Column.

The demonstrations caused traffic to be severely hampered along Westminster Bridge and Parliament Square, as well as Waterloo Bridge Roundabout.

Youngsters have also today staged events in other British towns and cities including Edinburgh, Canterbury, Oxford and Cambridge.