Can you still strike when on a contract that says you can’t strike?

I’m not asking for myself but on behalf of my colleagues and this is for the UK. So I work at a company called “Before”, and I’m not going to say the real name of company due to slander or whatever. But the Before drivers are on a contract that has a clause saying they can’t go declare strike action, basically another level of HR. I’m still trying to figure out worker’s rights and whatnot but this is pointless right? Can they go on strike even though the contract says otherwise? Is it not a right? Thanks.