Three Extinction Rebellion protestors were arrested after they chained themselves to a drilling platform on the Thames to protest a planned road tunnel under the river.

Activists staged the demonstration on Saturday (July 25) – and vowed to continue disruptive action when construction starts.

Silvertown tunnel will connect the Greenwich peninsula to the Royal Docks in Newham, and is expected to open in 2025.

The Mayor of London, Sadiq Khan, claims it will ease congestion around the existing Blackwall Tunnel.

But activists fear it will increase traffic and worsen pollution in some areas – and say the Mayor should consider a high toll on the existing crossing.

READ: Construction set to start as TfL signs off Silvertown tunnel

In a step change in direct action, three protestors boarded a Thames drilling rig early on Saturday morning, and unfurled a banner reading “No toxic tunnel”.

The protestors attached themselves to the platform by the neck using bike locks, and sent the keys to the Mayor with a letter asking him to come and talk with them.

The rig is believed to be carrying out preparatory work for the tunnel ahead of construction – though this has not been confirmed.

Police were quickly on the scene, but protestors were not removed for 11 hours.

A Stop the Silvertown Tunnel Coalition spokesman said demonstrators had showed they “will not take it lying down” when construction starts.

East London and West Essex Guardian Series: Protesters set off for the rig at dawn on Saturday (Photo: Extinction Rebellion Greenwich).Protesters set off for the rig at dawn on Saturday (Photo: Extinction Rebellion Greenwich).

He claimed there are “clear gaps” in the business case for the tunnel, and said the environmental impact will be serious.

“If you look at all carefully at the economic case for Silvertown the benefits just disappear,” he said.

The scheme is “entirely inconsistent with City Hall’s own carbon targets”, he added – arguing that a new road will increase traffic, and stop the Mayor reaching net-zero by 2030.

The spokesman accused City Hall of keeping the project “under the radar” and pushing it through despite local objections.

He said many people are unaware of the £1.2 billion scheme, but there is significant opposition.

Five boroughs near the planned tunnel are against it, with Hackney and Newham particularly vocal and Southwark, Lewisham and Greenwich also opposing the plans or calling for a pause.

Only Tower Hamlets supports the scheme – though all six councils are Labour led, aligned with the Mayor.

“We see no evidence at all of any support for this scheme in the communities,” the spokesman said.

READ: Silvertown protestors stage 'die in' demo at City Hall

Many Transport for London (TfL) investments are now at risk because of strain on the network’s budget in the wake of coronavirus lockdown.

But Silvertown Tunnel will still go ahead because it does not incur an upfront cost – the scheme will be paid for by contractor RiverLinx consortium, with the transport authority paying back costs after it is complete.

Last week the Government launched a review of TfL’s long term finances, with Mr Khan announcing his own independent review – and Silvertown protestors say both should consider the future of Silvertown.

A spokesperson for the Mayor confirmed that the tunnel will go ahead, arguing that existing infrastructure is “antiquated and worn out”.

The case for the scheme has been peer reviewed and a public consultation was held, they said.

“It is possible to reduce congestion and improve river crossings in the east of London while also tackling air pollution,” they added.

“Introducing tolls on both the Blackwall tunnel and at Silvertown – and the extension of the Ultra Low Emission Zone from 2021 so that Silvertown will be within the area covered – will play a crucial role in tackling congestion, improving overall air quality and providing much-needed additional bus services across the river.”