Joao Felix & Antoine Griezmann: Meet the lender behind the some of football's biggest transfers
A few steps from London's West End, and just a couple of miles from the capital's financial district, is a company helping football's elite seal some of the world's biggest transfers.
Joao Felix moved from Benfica in Portugal to Spain's Atletico Madrid as the world's second-most expensive teenager, thanks to a loan processed in trendy Fitzrovia.
"It was a strong summer for us, we were involved in some of the biggest and best moves," chief executive and co-founder Jason Traub told BBC Sport.
"We call ourselves a capital and solutions company for sport, music and entertainment - a sports bank, for lack of a better term.
"We help affect deals but we are not changing the way deals are done, or whether they do or don't ultimately happen. But we are certainly helping."
Traub, who spent 13 years with Investec Bank, and partner Stephen Duval, an Australian who previously worked with the Olympic Games and sports management company IMG, have made an impact.
Last summer's window saw a record £5bn spent across Europe's top five leagues, and they were involved in two of the biggest moves.
Atletico broke their transfer record for Felix just two years after moving into their £220m Metropolitano home.
Going to a lending company was an alternative way to fund his arrival without having to raise money by offloading French World Cup-winning forward Griezmann first.
'Distilling transfer-market pressure'
Barcelona took out a bridging loan to ensure they landed Griezmann in time for a money-spinning pre-season tour of Japan and the United States after their request for more funding from Spanish banks was reportedly turned down, having already borrowed more than £500m for stadium renovations.
"In truth, the real pressure at that time, for that transfer, was the start of pre-season, flying off to the Far East and the knock-on effects of not being able to unveil a superstar signing for the year as you land and what that would mean for exposure and sales. That impact was a factor for them," Traub said.
"We don't love being asked to make sense of transactions within a short timeline, particularly for those amounts, but for very good clubs that we know intimately and understand their credit strengths, if it makes sense we can move quickly."
Neither transfer was dependent on the other and so the domino effect which can often define a transfer window was reduced.
"In the old days you would have some of these deals happening in the last five days or even last five hours of the transfer window," Traub said.
"Don't get me wrong, we've all been glued to the TV watching the reporter in a car park waiting for that first deadline day move to happen and loved it.
"But it is not helpful or good for the game to rely on that first shot across the bow. So now clubs have a better means to a credible finance partner and are not as reliant on waiting for a Real Madrid, Barcelona or Manchester United to make that first payment to allow the rest to follow.
"We have distilled down the pressures that used to exist. Taking away some of that pressure in negotiations is much healthier in any event."
Helping clubs finance transfers or stadium improvements by lending against future broadcast income and the value of players as intangible assets is nothing new, and there are a number of lenders to whom clubs can turn.
Traub says an already established relationship with Benfica, having helped restructure their balance sheet, played a part in their involvement in the Felix transfer ahead of others "desperate to try to help because it was an opportunistic transaction".
He continued: "In this market place there are a number of brokers and banking groups that see this as a quick way to make money because they see these deals as being very visible and you might not need a world of credit expertise to understand that Barcelona or Real Madrid, at face value, will pay you back next year for a transfer."
Football finance expert Kieran Maguire, of the University of Liverpool, describes the firm as a "boutique" lender that has spotted a gap in the industry.
"They have realised that the transfer market and the club transaction market is unregulated, often unprofessional and contains people who see football as an opportunity for an easy profit. If anyone can then come in and run a professional service and effectively provide a one-stop shop, then there is a gap in the market," he said.
"Whether that will be successful in generating the level of income they are looking for, I'm not so certain because football is a very insular industry and there are unusually close relationships between agents, management and clubs, and that particular dynamic will be difficult to break.
"But for clubs that do operate with integrity and do things by the books, then there is potential for a company like 23 Capital to be involved.
"A boutique operation, and that is what they are, don't have to go through so many layers of approval, don't have to go through governance rules you may see at JP Morgan, where a bank of that nature is very risk concerned and will have a compliance department, which to a certain extent is the tail wagging the dog in corporate lending."
When Traub and Duval went about founding a business that could work as effectively in football as it could in Formula 1 and tennis or the music industry and in Hollywood, they did so with a 'high end' focus.
Traub says more than £2.3bn has been provided by 23 Capital since its inception, evenly split between sport and the entertainment industry - in which they have provided finance for the Kobalt Music Group, which has Childish Gambino and the Red Hot Chili Peppers on its roster, and holds publishing rights to the late Elvis Presley's recorded work.
Since its beginnings in London in 2014, the company has expanded to open offices in Barcelona, New York and Los Angeles.
"We have always wanted to position ourselves very much in the blue chip," Traub explained.
"We have been able to get great traction at the very top and a profile with industry leaders in the three sectors.
"A real challenge was how we saw ourselves. We wanted to be principal lenders, we wanted to build our own balance sheet, we didn't want to be brokers or fund managers for other people - we effectively wanted to set up a banking model so that we could own that risk."
With backing from billionaire philanthropist George Soros, Traub and Duval got the business up, running and positioned where they wanted.
Ensuring they made a success of it took a considered approach to recruiting in an effort to become "pure play" or specialist lenders across sport, music and entertainment.
"We have pulled individuals from places like Universal Music, people who have worked in football, within the business as much as pulled credit specialists," Traub added.
"We are a business, not unlike a bank in some ways. But an individual at a bank may get a deal done because they can get a bonus at the end of the year or maybe go to a different bank if it doesn't work out - but this is our livelihood.
"We are truly aligned to our clients, the football industry, to drive value for them in a symbiotic relationship, and that is what credit should be."