LONDON — National, or international?

As the fault lines deepen between these two ways of thinking in Western democracies, wealthy buyers are facing a similar choice when it comes to acquiring art.

The London Art Fair, whose 30th edition opened to V.I.P.s on Tuesday in the Islington district of the British capital, has, in recent years, become best known as a showcase for dealers in “Modern British,” meaning works made by British artists during the 20th century.

“I used to bring contemporary, but now the standard of Modern British is higher, so I bring historical pieces,” said Jane England, the Australian-born founder of England & Company, a London dealership that has been exhibiting at the fair since the early 1990s.

“Before Frieze, this fair had a different profile,” Ms. England added, referring to the Frieze art fair, which made its debut in 2003 and has come to be regarded as London’s premier international event for new art.