LONDON—This season’s most anticipated painting was a long-lost and well-preserved fête galante by Jean-Antoine Watteau. Painted around 1718, La Surprise, depicting a guitarist and an amorous couple, was previously known only through a contemporary engraving and a copy in the Royal Collection at Buckingham Palace. It came to the block at Christie’s on July 8 with an estimate of £3 million to £5 million ($5.9–9.8 million). Just when the battle among the half dozen or so bidders seemed over, the London dealer Luca Baroni raised his hand to claim the prize for £12,361,250 ($24.4 million), a record for any French Old Master at auction. This was one of the few high points in an otherwise lackluster sale, in which more than a third of the lots were passed and many others sold on one bid.  

Notable works included William Larkin’s highly decorative 1617 three-quarter-length portrait, probably of Lady Thornhagh (est. £400–600,000; $790,000–1.2 million), which went to the London dealer Mark Weiss for a record £505,250 ($996,000). Another big sum, £373,250 ($736,000), was paid by the New York dealer French & Co. for Thomas Lawrence’s 1797 oil sketch of his mother (est. £50–80,000; $98,000–160,000).

Perhaps the most unexpected price of the evening was the record £3,065,250 ($6 million) paid for Anthony Van Dyck’s surprisingly dull Rearing Stallion, 1620–22/23 (est. £1–1.5 million; $2–2.9 million). One suspects it was purchased for its subject matter, as the same telephone buyer also secured the next lot, George Stubbs’s Antinoüs, a Chestnut Racehorse, in a Landscape, circa 1760s (est. £250–350,000; $490–680,000), for £337,250 ($665,000).

The mammoth Sotheby’s sale the following evening could not have been more different. Most lots were hotly contested—58 percent achieved prices, including premiums, above their high estimates—and 19 artists records were set. Indeed, the final total was the second highest for any single-session sale of Old Master paintings at Sotheby’s London, after the £67,584,510 ($104.7 million) made in July 2002, when Rubens’s Massacre of the Innocents sold for £49.5 million ($76.7 million). The buyer base exhibited “extraordinary breadth,” says the head of department, Alex Bell. A substantial 28 percent of lots went to U.K. buyers, 45 percent to Europeans and 13 percent to Americans.

The season’s other great rediscovered painting, besides the Watteau, was Frans Hals’s circa 1638 Portrait of Willem van Heythuysen (est. £3–5 million; $5.9–9.9 million). It was the evening’s top lot, selling for £7,097,250 ($14 million) to the London dealer Richard Nagy. A less-expected success was Lucas Cranach the Elder’s David and Bathsheba, 1534 (est. £200–300,000; $396–595,000), which was bought by the London dealer Colnaghi for £2,113,250 ($4.2 million).

The Misers, one of the finest among the vast number of copies of a famous lost original by Marinus van Reymerswaele from the early 16th century, came to the market for the first time since the the 18th century. It soared past its high estimate of £150,000 ($297,000) to achieve £2,057,250 ($4.1 million), even though not much is known about the artist, thought to be a follower of van Reymerswaele. “There was evidence throughout the sale that buyers were prepared to pay high prices for strong images and high-quality paintings without a name,” says the specialist George Gordon.

The overall excellence of the offerings was due in large part to its three single-owner collections, not least that of the German collector and philanthropist Gustav Rau. A highlight was his beautifully preserved circa 1400 gold-ground devotional triptych by the Sienese painter Taddeo di Bartolo (est. £300–500,000; $595–990,000), which fetched a record £1,889,250 ($3.7 million). Additional records were set that evening for Jan Brueghel the Elder (£3,513,250; $6.9 million), Aert van der Neer (£2,729,250; $5.4 million), Guido Reni (£1,833,250; $3.6 million) and Frans van Mieris the Elder (£1,329,250; $2.6 million).