A former chartered civil engineer has come up with an alternative Option A for the lower Thames Crossing.

Ken Bowman, now 82, spent years designing tunnels and previously worked on the Victoria tube tunnel and the initial widening of the A2 to make it a dual carriageway.

While he concedes much has moved on since his heyday, he said Highways England’s Option C plans have left him “baffled and disillusioned” as it does not address the problem of traffic in Dartford and there is another solution; with a variant to Option A.

His proposal is a twin bored tunnel – similar to what is already planned east of Gravesend – to be constructed in Dartford.

It would connect Darenth (junction 2) south of the A2, to South Ockenden in Essex, north of the A13.

The length would be about six miles each end and would emerge in semi-rural country.

During a meeting at St John's school in Gravesend last week Gravesham council leader Cllr John Cubitt laid out a similar plan.

He said: “What needs to happen is a joining on the m25 to the m25, with a six mile tunnel, like they have going underneath Paris. It shouldn’t be beyond us to build a similar tunnel. We just need to go under the whole goddamn lot.”

“What needs to happen is a joining on the m25 to the m25, with a six mile tunnel, like they have going underneath Paris. It shouldn’t be beyond us to build a similar tunnel. We just need to go under the whole goddamn lot.” - Cllr John Cubitt

Afterwards, he added: “Having a tunnel joining the motorway from junctions further away, Darenth and Ockendon, would be better for everyone. It would be better for people in Dartford because they wouldn’t get the pollution and it would be better here because it would not destroy the countryside, or people’s homes.”

Mr Bowman said the current Highways England plans do not address the inadequacy of the existing Dartford crossing.

He said: “Their proposals for an additional crossing further downstream are presented in some way as a solution to this problem which they clearly are not.

“They argue the economic case for its construction and I accept that it would be a useful addition to the road network. But what is it we are being offered? A measly 14% diversion from Dartford to this new crossing in a decade’s time.”

He said that as traffic overall was likely to have increased by more than that by the time the new crossing was built, people were ‘being offered absolutely nothing’.

He continued: “Highways England when considering the possibilities at Dartford characterise it as ‘a road widening scheme’ and viewed in that light the mind boggles at the complexity of tackling this while the crossing is running live. I have every sympathy with them in shunning this approach.”

Instead, he suggests connecting junction 1 with South Ockenden, as it would by-pass the local traffic system in Dartford.

Highways England’s current Option C tunnel proposals could cost almost £6 billion.

Mr Bowman has used the Western Scheldt Tunnel (Netherlands) as the closest example to cost up his own plan, which comes in much cheaper.

Built in 2003 the tunnel cost €726 million and is 4.1 miles, bored.

Mr Bowman said: “I’ve see a claim made that it is the deepest underwater tunnel in the world, so it was a seriously big project.

“I have not examined the comparative geologies but based on this and admitting to some highly speculative costing it indicates that my proposal could be enacted for about £1bn.

“Even if we are not as good as the Dutch it can be seen that there is plenty of leeway between £1bn and the £5bn cost of the Highways England proposals, so at the very least it must be worthy of further study.”

He said if considered, his plan would reduce journey times, have no ecological damage, negligible land and property acquisition and no interruption of traffic during construction.

Mr Bowman intends to submit his ideas to Highways England as part of the public consultation, which ends on March 24.