LONDON (Reuters) – Greenpeace activists boarded a ship arriving in Britain on Thursday to stop a consignment of over 1,000 Volkswagen (VOWG_p.DE) cars from Germany whilst others sought to immobilize vehicles at a port in anti-diesel protests.

VW admitted cheating in diesel emissions tests in 2015, triggering political and consumer pressure which has seen diesel cars sales slump in major markets and politicians around the world announce plans to ban the sale of conventional vehicles.

Greenpeace said its volunteers had used kayaks and boats to board the ship in the Thames Estuary in a bid to stop it unloading at the southeastern port of Sheerness in Kent.

They were hanging from the ship’s 27-metre-high unloading door, refusing to leave until VW agrees to take the cars back to Germany, it said.

Other protesters broke into a vehicle park at Sheerness where they were sticking labels on engines and attempting to immobilize cars by taking the keys, the environmental pressure group added.

Peel Ports Group, which owns the site, said protesters had illegally entered secured areas of the port and it was working with police, Greenpeace and VW to resolve the situation.

A VW spokesman said around 1,200 cars were on the ship including diesel, petrol and hybrid models.

Britain aims to ban the sale of diesel vehicles from 2040 as part of plans to improve air quality but activists said the measures needed to be implemented now.

“Diesel cars are toxic – so we’re here to block VW imports on behalf of all of the children who are the most acutely affected by the health impacts,” said 38-year old Janet Barker, who took part in the protest, in a statement.

“The government says we need to wait another 23 years for dirty diesels to be banned. We can’t wait that long,” she added.