The arrest earlier this week of Navinder Singh Sarao, the trader alleged to have made $40 million through manipulation of futures markets, has put the UK's "trading arcades" business in the spotlight.

It was at one of these arcades - one-stop shops where traders can rent desk space, computer systems and undertake training courses in return for a fee and a share of any profits - that Sarao learned his craft before eventually branching out on his own.