In 1929, the documentary photographer Margaret Bourke-White took a series of shots of the lobby of the First National Bank of Boston. Lowering and under-lit, these show, among the bank's marbled arches, murals painted five years earlier by Newell Convers Wyeth, known as "NC".
Five years later, Bourke-White would become famous for her images of the Dust Bowl, nature's metaphor for the Great Depression. In 1929, though, that disaster was just beginning, marked by runs on banks such as this one. Bourke-White's dark vision seems oddly prescient. The same can not be said of Wyeth's.
The Boston bank wall paintings showed gallant little ships plying their way through history, from Phoenician biremes and Elizabethan galleons to modern tramp steamers. Brightly coloured and optimistic, NC's murals have the feel of John Masefield's quinquiremes of Nineveh and dirty British coasters. Perhaps they were based on them. Like Masefield's poem, "Cargoes", Wyeth's paintings are a stirring hymn to trade, to the beneficence of commerce. Scarcely had their paint dried than capitalism encountered the squall that seemed likely to sink it forever.
Given the current economic climate (not to mention current attitudes to bankers), it is brave of Bank of America Merrill Lynch to have lent these pictures to the Dulwich Picture Gallery. BAML owns a collection of the work of the Wyeth family, titular heroes of Dulwich's new show. NC's son, Andrew Wyeth (1917-2009), has some claim to being the best-known American figurative painter of the 20th century; his grandson, James Browning Wyeth, known as Jamie, now in his sixties, is also an artist. For all America's meritocratic claims, I can not think of a British art dynasty to match the Wyeths, any more than I can imagine the son of a British premier following his father as the next prime minister but one. As both the Wyeths and the Bushes show, American inheritance is not necessarily a matter of talent.
Perhaps the most interesting thing about NC Wyeth's little ships – about his work in general – is their link to commerce. They are, in more senses than one, commercial art. Pretty well all of the pictures in the opening section of The Wyeth Family are illustrations to stories: Mark Twain's The Mysterious Stranger, Washington Irving's Rip Van Winkle, novellas by Sir Arthur Conan Doyle. Quite what relation these full-size paintings, many in egg tempera, bear to NC's book plates is not revealed by the literature accompanying this show. Are they studies? More to the point, do we care? The Dulwich exhibition shows NC Wyeth to have been at best a mediocre commercial artist, at worst the maker of such curiously revolting images as Untitled (Marines landing on the beach): part Teddy Roosevelt, part GI Joe and entirely missable.
Given the show's title, I feel I'm not giving anything away by saying that Jamie Wyeth follows, all too closely, in his grandfather's footsteps. I wouldn't have thought it possible for a contemporary painter to make a work such as September 11th 2001, but there it is for all to see. JB Wyeth's picture adds to the dreadfulness of that day with a horror of its own. Based on Joe Rosenthal's shot of US marines on Iwo Jima, this picture evokes a glib patriotism I assumed – hoped – had disappeared with Vietnam. I very much doubt it would be hanging in Dulwich Picture Gallery had Wyeth's surname not been Wyeth, any more than I imagine JB could have painted portraits of Rudolf Nureyev (included in this show) or of Andy Warhol (sadly not).
Which leaves the missing link of Andrew Wyeth, the only reason I can think of – and not a very good one at that – for going to this exhibition. It is often said that Andrew Wyeth divides US critical opinion, although I'd guess that division is along regional lines. (New York and Los Angeles hate him, Middle America loves him.) The banker Abraham Mendelssohn – child of the philosopher Moses, sire of the composer Felix – once sadly remarked: "Formerly I was my father's son, now I am my son's father." Andrew Wyeth was at least spared that. Of the three, he is the only Wyeth with any shred of originality, albeit of a loopy kind. His Antler Cross (1983) is hauntingly composed and well painted, and a couple of his other pictures are intriguing. Tickets to this show cost £9, though, which works out at £3 per interesting picture. A walk in Dulwich Park is free.
To 22 Aug (020-8693 5254)
Charles Darwent digs out his water wings to visit Ernesto Neto's new show (including swimming pool) at the Hayward Gallery