Had three interviews in total:
HR interview:
Positive experience, seemed very organised and just asked general questions (i.e. why did you want the job). Discussed perks of the company, which are good. Came across very professional. No preparation can be done for this stage.
1st interview with consultant:
Very passionate but completely incoherent interviewer, came across as if they hadn't slept in several days. We chatted about general physics for most of the interview, then they asked one classic undergraduate physics questions: just an exercise in calculus. Wasn't clear what they were looking for. This person clearly enjoyed working here, but came across overworked. They discussed example projects, which sounded dull given my expertise.
2nd interview with consultant:
Turned up late, hadn't read my CV and was completely unprepared, so much so it was either an Oscar winning performance or they really were not expecting to interview me. The interviewer just sulked for the whole interview. Curious to the reason for their bad mood I asked them 'Do you enjoy working here'. They replied 'No', giving reasons of being overworked and the not enjoying the projects they were working on. They did say they used (over 5 years ago) to enjoy working here.
Comments:
I went here with an offer from a similar company and was glad to accept this offer on the way home from the interview, happy in the knowledge I wouldn't (personally) want to work with TTP. That being said, I think it is worth interviewing with TTP, you will get an idea if its right for you, particularly as they reimburse travel expenses. If its right for you it may be great, but it seems like you will be worked hard if you were to join.