The project may seem far-fetched however at it's shortest the bridge will be 33. 7 kms long.
The longest bridge in the world, the Donanyang-Kushan bridge in China, is over five times this length.
Engineer Ian Firth explained the challenges of building any future bridge:
“It’s a very very busy shipping channel we all know that and by and large the ships are separated. So ships going one way and the other way are separated in different channels. You’d have a very long span where those navigation tunnels are (where the ships would go).
You’d almost certainly have to have vessel impact protection around the supports of the bridge so if anything hits it, it doesn’t bring the bridge down.”
It's not the first time Johnson has had an ambitious bridge plan.
The London Garden Bridge project was scrapped by Johnson's successor for Mayor of London Sadiq Khan after £37 million pounds was spent on the project.
But Ian says a channel bridge might be more likely:
“He’s making a very interesting political suggestion that improving our connections with Europe is a good idea particularly in the light of Brexit. As a bridge designer I obviously would welcome the opportunity to build a bridge. I’ve done similar things, I’ve worked on similar projects so I know it’s feasible.”
Downing street officials say there're no concrete plans to begin construction.