Pros
I wasted several months of my life on this company and suffered panic attacks at their toxic behaviour, I am not going to say anything positive.
Cons
I only worked at think tank maths for a short time and what I experienced was shocking. There is a toxic culture of sexism, overwork, and irrational behaviour from management. The management, who are the publicly facing image of the company, are a married couple which is a huge red flag. They openly insult staff and only come into the office late despite having strict rules for everybody else. They do not understand the technical work but they pretend that they do. I am embarrassed that I did not realise this during the interview because I assumed that they knew much more than me. It is very stressful because we all have to pretend that the publicly facing "chief mathematician" is technical, when he has no clue about basic mathematics. All the other researchers were fresh out of university which is another red flag because no experienced person would put up with this.