Having recently gone through the above process for my local force I am in a position to offer insight into the Police Service selection process, commonly known as the Assessment Centre. Now run by NPIA. I cannot give any details of the written exams or scenarios (They make you sign a disclaimer), they changed in November anyway, but can attempt to brush any public shoolboy rumours aside. Any takers/interested parties, please send me a PM and once coms are established will send an email, revealing the finer points of the process. I am by no means an expert, but passed with points to spare. Incidentally most forces have just lowered the pass percentage rate to 50%. Although some, like mine are refusing to budge. Good for them.