What would happen if you blew up an atomic/hydrogen bomb in the english channel tunnel?

( Assuming this attainment would be possible) What kind of harmful goods would take place immediately/after a explosion?

The tunnel walls would collapse and the tunnel would flood. That’d be about it.
there would be no tunnel….
It would not destroy all the tunnel , but a part will be broken and the tunnel wii be full of water so unuseful
According to a (fiction) book I read recently the tunnel collapse would create a tsunami like wave that would devastate coastal Europe.

There probably would be some kind of surge and it would certainly mean the end of the tunnel’s use.