The lowest-priced deposit box at IBV International Vaults is only 5cm high, 16cm wide and 49cm deep. It costs UK£600-a-year-to rent and an entire room can be hired for UK£2.5m a year.

“We won’t deal with millionaires,” said Sean Hoey, managing director of IBV International Vaults London. “We will be dealing only with billionaires.”

IBV International Vaults was formed in 2004 and marketed itself as the world’s most exclusive private vaults.

Its flagship premises for billionaires is in the Grade II listed Stanhope House, formerly Private Barclays Bank, in London’s Mayfair. The striking building will open for business for billionaires next week with 3,300 safety deposit boxes.

“We are the most expensive safety deposit box in London; actually, in the world,” Hoey told The Guardian. “But you know the saying, ‘You get what you pay for,’ and the customers here will be king.”

The lowest-priced deposit box at IBV International Vaults is only 5cm high, 16cm wide and 49cm deep. It costs UK£600-a-year-to rent. That compares to UK£465 for a box twice the size at Harrods, and £240 in Metro Bank – the UK’s largest supplier of safety deposit boxes with 150,000 boxes in total across 70 branches.

Hoey told The Guardian that the smallest box is big enough to store an array of jewellery and “a fair few gold bars – they’re only the size of your mobile phone”. If billionaires have a lot of gold bars there are boxes the size of filing cabinets, and a whole room can be hired for UK£2.5m a year. “We have had a few enquiries about it,” said Hoey.

IBV International Vaults, which is owned by South African multimillionaire Ashok Sewnarain, said it was opening the London vault due to spiking demand from the world’s wealthiest people for safety deposit boxes, in fear of a possible reaction against rising inequality. IBV bring its other services, including the IBV Gold, IBV Supercar Club and IBV Rolls-Royce service, to the city.

“Clients of IBV London can be expected to enjoy more than just the use of the Vault. Our vault clients globally, including those in Switzerland, Dubai and South Africa, have come to enjoy high end lifestyle benefits in addition to their vault lease. IBV London will be no exception as one of such offerings is that our clients can expect to be collected in a chauffeur-driven luxury supercar to the high security vault, where they will arrive to an opulent entrance, complete with a 24 carat gold flecked pavement and greeted by a member from IBV,” said Sewnarain.

“Our clients can also expect to enjoy preferential rates for the purchase of gold coins and other numismatic coins from our vault facility. The look, the feel, the experience that IBV will bring to its London clients is sheer luxury.”

Hoey said the bank vault will be more like an “exclusive private members club than a bank”.

Sewnarain has bought a Rolls-Royce with the number plate II IBV, which can be booked to ferry customers to and from the vault. IBV’s advert for a chauffeur to drive the Rolls states: “Our clientele is the UHNW (ultra-high net worth). IBV London requires the experience and professionalism of a well-trained chauffeur to welcome and drive our high-profile/esteemed clientele to their desired destination.”

When clients arrive at IBV London, they will be met by two doormen who will guide them through the security which includes fingerprint and iris scans to open doors to the basement vault. “White-gloved custodians” then help customers to their boxes.

“This is an important landmark opening for the IBV Group, to have its flagship headquarters positioned in London, demonstrating the company’s commitment and belief in the UK as a key financial centre,” said Hoey.

Sewnarain has previously set up billionaires’ bank vaults in South Africa, Switzerland and the UAE.