They call it the bat cave, and its the most exclusive car park in Britain.

Inside a secret west London underground bunker there are rows of Aston Martins, Ferraris and Rolls Royces hibernating under blue blankets while their millionaire owners are away.

It is easy to see the appeal of the high security vault: safe from the attention of thieves, tourists and – in one or two cases – wives, Londons wealthy petrol heads can hide their prized toys in here without worry.

The luxury goods are kept in a dehumidified, climate-controlled environment with daily pampering from a team of car butlers who also offer chaperoning and chauffeuring as part of their service.

Read more: Should the rich be taxed more?

"Were professional babysitters" says Tim Earnshaw, founder and boss of Windrush, the company behind the business.

So tight is the security that even Earnshaw gets the entry code to the high tech keypad by the car park entrance wrong on first attempt: "I put in last weeks code" he laughs.


A row of Aston Martins underneath soft breathable blue covers

When we do get through the gate, the near-200 spaces are almost full; a sign of Earnshaws success in bringing the brand to London after running a similar venture in The Cotswolds where he first started by offering to store cars on his farm 15 years ago.

But after three years of growth in the capital, Earnshaw reveals that he is now planning a second London bat cave of a similar size: this time, closer to the Square Mile.

"Were in negotiations for a new place…were listening to the market," he tells City A.M.

A move east reflects Earnshaws own confidence in demand from the majority of his London clientele: those who work in the financial sector.

Hedge fund managers, senior lawyers and even several FTSE bosses are among the corporate clients who park their Porsches or Maseratis here at a cost of £500 a month, often to pick up on a Friday afternoon before driving to their country house.

One London property developer even keeps several luxury cars parked here which come above ground when clients want a ride to a house that is on sale.


Windrush founder Tim Earnshaw is now setting his sights on another bat cave nearer to the Square Mile

"City customers always have targets, whether its floating a company or opening new branches. They want nice cars as a symbol of the fruits of their labour for when they hit those targets."

With the typical car in this room costing £200,000, most of these fruits certainly do not come cheap. Yet considering the price tags involved, what is perhaps most surprising about the Windrush business is its lack of flashiness.

"We dont tend to look after those who cruise around Central London," says Earnshaw, in a subtle indication that the underground lair is for car enthusiasts, rather than the ostentatious drivers who have made headlines in recent years for racing gold-tinted sportscars down the Kings Road.

"We have £25,000 classic Fords sitting next to £500,000 Aston Martins. You leave your wealth at the bank account," he insists.

Read more: Revealed: The world's wealthiest billionaires

A former logistics manager at Ferraris F1 team, Earnshaw is himself a car-obsessive who seems keen to keep business the way it currently is: "We havent sold out to inveRead More – Source