ThinkTank Maths interview questions

Awful. Dehumanising experience, lasted around 3 hours - would not recommend. Almost no interaction with the interviewers. It was basically a really badly formatted maths exam, conducted on Skype. You had to answer maths questions on paper (in silence whilst they muted their microphone) then hold up the solution to the Skype camera which they would then copy down. I got told of for smiling at the ridiculousness of this by one of the interviewers. There was zero discussion about your solution - which was a stated policy of theirs. No description of the company, questions about yourself or why you wanted to work there. They then had the audacity to ask how I had found the interview format at the end. They seem to not understand that an interview is a two way process.