Both contestants in Countdown have 30 seconds to find the longest anagram that is also a valid entry in the Oxford English Dictionary. The one with the longer valid word wins, gaining equal points if there is a tie.
There is always an expert in "Dictionary Corner" who attempts to find the longest possible word, usually something obscure.
There are also two special rounds. One is mathematical (pick a combination of 6 large and small numbers -- large = {100,75,50,25}, small = {1..10} -- and attempt to make a randomly generated three-digit number using only addition, multiplication, subtraction and division. The other is a 9-letter handcrafted anagram which always has a 9-letter solution.
It would be interesting to have a bot that used information on word frequency in common vocabularies/usage to guess what the contestants were likely to find, vs. the expert with an open-book. I imagine few people would find 'perfectos' but many more would find 'prefects'.
Having said that, I'd imagine most people going on the show -- especially at this stage! -- would be armed with many more obscure words than the average reader. (I auditioned back when I was 16, in fact, but failed at the anagram round. Oh well! Growing up 'playing' Countdown certainly made for a fun childhood, and I was frequently called Carol at school because I was good with numbers. :))