Sadiq Khan’s office has been accused of trying to ‘silence’ scientists over publishing research that showed his ultra-low emissions zone (Ulez) policy had ‘insignificant’ effect on pollution, as protestors brought traffic to a standstill on Saturday to fight against expansion of the scheme.

The claims were made following a series of emails between Shirley Rodrigues, the London Mayor’s deputy for environment and energy and Professor Frank Kelly, director of Imperial’s Environmental Research Group, which has received £800,000 of funding from the London Mayor’s office since 2021.

In the emails, seen by The Telegraph, Ms Rodrigues said she was disappointed that Imperial College had published a study by the Department of Civil and Environmental Engineering that showed Ulez cut nitrogen dioxide by less than three per cent and had achieved an insignificant impact on ozone and particulate matter.

Such research undermined the London Mayor’s policy, argued Ms Rodrigues.