Activists demanding action over air pollution in London have scaled a number of the capital's most famous landmarks in a mass protest.
Greenpeace UK posted images across social media showing dust masks and mock gas masks on statues of Oliver Cromwell, Queen Victoria, Eros, Winston Churchill and Horatio Nelson.
Four protesters were able to get past security at the Houses of Parliament to scale the state of Cromwell within the grounds of the Palace of Westminster.
Police were called at 6.25am as a man and a woman, in climbing gear and hard hats bearing the Greenpeace logo, put a face mask over the statue.
A Met Police spokesman said: "The two people on the Cromwell statue have come down, they have been arrested.
"Four people in total have been arrested in connection with what has been going on."
Greenpeace released images showing more protesters climbing the 52m-tall Nelson's Column in Trafalgar Square, adding it was "quite a view from the top".
The organisation said it had targeted a total of 17 statues across the city, also including those of Thierry Henry outside Arsenal's football stadium and Sherlock Holmes outside Baker Street Tube station.
Campaigner Areeba Hamid told PA the protest was timed ahead of the upcoming London mayoral elections: "Monitoring shows that, if these statutes were real people, many of them would often be breathing dangerous, illegal air.
"That's why we've given them face masks. Of course many millions of Londoners, including kids, are breathing that same air. Kitting everyone out with face masks is not the solution; instead we need to see real political action from the new mayor.
"We need a clean air zone covering a large part of the city. Whoever wins the election has to stop the talk and start the action."
