As the project of a tunnel under the Channel date back to the XIXth century, I was just curious if this had been the case ?
And if so, why was it dismissed ?
No, it would have made no strategic or tactical sense. Even assuming it was technically possible at the time - a big assumption - the resources and manpower required would have been enormous, and of far more use elsewhere. Plus, even in the 80's, it took 6 years to build. Additionally, it would have been almost trivially easy to counter a single beachhead.