With 189 clients to Numis's 195, this is the first time that JP Morgan Cazenove has ever lost its crown since Adviser Rankings began collecting data more than 13 years ago. It has lost four clients since May.
There was some solace for the dethroned broker, as it regained its lead on the number of FTSE 100 clients on its books from Bank of America Merrill Lynch (Baml) which held the position for just over a year.
Baml lost Worldpay as a client, and saw Hikma Pharmaceuticals and Intu Properties relegated to the FTSE 250. Meanwhile JP Morgan added G4S in the FTSE reshuffle.
FinnCap had the most Aim-listed clients, although Numis also reared its head in this market with its clients adding up to the largest aggregate market value.
Corporate brokers in the UK are referred to for a variety of reasons, from advising on acquisitions to listing on the stock market.
Brokers are currently facing uncertain times, as the new Mifid II regulations which come into force in January threaten to upend the industry.
Financial adviser rankings
With 100 clients, FinnCap took top spot among financial advisers for the most stock market clients. Numis retained second position while Cenkos Securities moved up to third.
JP Morgan had the most FTSE 250 clients, while Baml claimed the most on the FTSE 100.
Law firm rankings
A similar upset to that in the brokers' lists disturbed the law firm rankings, as Slaughter and May relinquished its top position for number of clients for the first time in nine years to Herbert Smith Freehills. Slaughter and May did hold on to the most FTSE 100 clients, with 33.