Well I think its time we start thinking outside the box. First, a couple of facts.
1) A its narrowest point, the English Channel is 19 miles wide and about 150 feet deep.
2) A cubic foot of hard soil weighs about 80 pounds.
So if the French army was to build a 19 mile land bridge across the the English channel that was 150 deep and 40 feet wide (wide enough for wagons going both ways and the occasional redoubt with artillery to fight the British Navy), it would take 601,920,000 cubic feet of soil, which weighs approximately 24,076,800 tons.
If the French army deploys a work force of 50,000 people and all the soil necessary is readily available and each laborer can carry 1 ton of soil a day, that means it would take the French 481 days to build the land bridge.
So if the French really, REALLY want to invade England, it would take them about 1.3 years to achieve victory (and that's without a navy).
If we use math, ANYTHING is possible.
If this was actually realistically possible, I could see the horror in England as the French juggernaut slowly inches forward across the channel. It would feel like a modern example of Alexander's siege of Tyre.