Background checks: yes.

Drugs checks: why?

I know that when applying for a UK government position (be it temporary or permanent) that they do a check for various things to ensure that you are a low blackmail risk e.g. searching for evidence of financial problems (including gambling), substance abuse (legal or illegal), criminality etc.

Luckily for me, if I had any noteworthy habits or pastimes then I have left them all in with my youth. And regardless of whether I had any or not , I have not picked up any as I got older. All of my oddities and pastimes fit into the category of ordinary (but not necessarily "normal" 😉 ).