The king of Brit Art extends his empire

Here is a list of some of the household names of contemporary British art: Tracey Emin, Damien Hirst, Gavin Turk, Antony Gormley, Mona Hatoum, Gary Hume, Gilbert and George, Sam Taylor-Wood and Jake and Dinos Chapman.

Do they have anything in common other than their ability to please, intrigue, shock and sometimes outrage us? Yes. They all have the same dealer, a silver-tongued old Etonian called Jay Jopling, the son of Michael Jopling who was Minister of Agriculture from 1983 to 1986 in Margaret Thatcher's second administration.

Yesterday Mr Jopling opened a new gallery space in Hoxton Square, east London, building a glass box on the roof of White Cube Two, which he opened in 2000. At a stroke he has almost doubled the building's exhibition space.

He has other, longer term plans too. He has just bought an old electricity sub-station in Mason's Yard, a quiet mews off Duke Street, St James's, virtually opposite the original White Cube gallery which he opened in Mayfair in 1993.

Now that Anthony d'Offay has closed his three West End galleries, Mr Jopling is arguably the most influential dealer in contemporary art in London – of the 40 artists in the "Sensations" show at the Royal Academy in 1999, a quarter of them were represented by Mr Jopling. Does influence equal financial success?

Mr Jopling goes coy when asked such questions. It is a private company, he says. He doesn't report his turnover publicly. He doesn't talk about profits either. So what about the price of the art instead?

There are two shows running in Hoxton this week; paintings by Gary Hume in the original, ground-floor gallery, and two pieces by an African-American artist, David Hammons, upstairs in the new gallery.

Hume, who represented Britain at the Venice Biennial in 1999 and recently had a retrospective at the Whitechapel Gallery in east London, is best known for painting thinly, in bright gloss paint, on aluminium. The subject matter is usually dream-like and romanticised – owls, faces, flowers. This time the colours are much more sombre – greys and blacks – and the imagery more inscrutable. The best of this new work is a series of charcoal drawings on canvas, clean black lines against a grey background. A Hume painting on aluminium will cost you a sombre sum of money too – somewhere between £45,000 and £75,000. One of two snowmen sculptures on display in Hoxton might cost £60,000.

Early in the 1990s Mr Jopling and others were called to the Tate Gallery for a brain-storming session with Nicholas Serota. What could be done to make this country less philistine about its artists, to make people sit up and take notice?

One answer was to encourage newspaper editors to ridicule the artists. That way people would sit up and take notice. The strategy worked – and Mr Jopling was one of those who made it work. And he made it work for those artists that he now represents worldwide.

"My role as a gallerist is to make sure that my artists' work is seen around the world," he said. "My responsibility is to artists, to our clients, and we have a great and growing responsibility to the public too. I like to think of White Cube as a calling point for information about contemporary art."