Reneg process

Call up the team that you were supposed to work with (likely your main point of contact if dealing with the team directly, else HR) and tell them you appreciate the offer but you want to persue soemthing else but appreciate the opportunity to work with them.

In the U.K. from my experience most places don’t care about a renege, if anything they’ll try to convince you to stay. Haven’t heard of anywhere that ‘hunts people down’ so don’t worry about it 

Risky

Do what those above have said— get in touch with your main point(s) of contact, explain your decision, and show appreciation for the opportunity. Obviously make sure you have a valid reason for reneging, though.

In all likelihood it won’t come back to bite you if you use common sense. Yeah, you will probably never work at that place, but I think it’s unlikely that they’d go out of their way to screw you unless you do something stupid like make a really long LinkedIn post about your new job or something like that. Just be courteous and don’t waste any more of their time.

I've always wondered, has anyone ever signed a 1st offer, reneged and signed a 2nd offer? Are there any legally binding consequences