When concentrating the brain uses less than 5% of it capacity the rest is automatic in times of stress the automatic fight or flight response takes over the OP did and said what his brain thought best and it worked.
Anyway that area and the alley way up besides House Of Fraser, the Cathedral and the shops opposite Snow Hill station is full of blaggers of all colours and nationalities.
It's a prime spot with a lot of workers and the bus stops sorry to hear of your experience and you did the right thing to survive extortion by a thug