Security theatre. What's the point of metal detecting you on eurostar? You going to hijack the train with your knife?

Cars and vans in the tunnel don't go through metal detecters, and you can smuggle a far larger bomb that you can in a suitcase.

But eurostar is the exception to the rule with security. I tend to aim to arrive at my mainline station about 5 minutes before the train leaves incase I get delayed on-route, but that's because I live in a small town which only has 1 train per hour. When I take a route with 3tph I don't bother looking at the times, just go when I'm ready and accept on average I have to wait for 10 minutes.