LONDON - Picture, price, provenance - typically in that order - is what grabs a potential buyer’s attention. Picture and price speak for themselves, provenance, however, can offer an extra dimension: by turn ‘gravitas,’ ‘glamour and spice' or 'by direct descent' - added values almost always impossible to quantify.

Museum quality is exactly what defines the lot shown on the cover of the catalogue for our next sale: Sorolla's Valencian Fishermen of 1895. The painting was immediately snapped up by the talented and innovative museum director, Hugo von Tschudi, for the Berlin Nationalgalerie in 1896 where it stayed for the ensuing 35 years – incontrovertibly blue-chip provenance for a landmark painting by Spain's foremost Impressionist.

Joaquín Sorolla’s Pescadores Valencianos (Valencian Fishermen). Estimate: £1,000,000 - 1,500,000.

Blue blood is the star dust that marks out the history behind another work in our sale – a preliminary oil for the Peder Severin Kroyer's 'blue period' masterpiece Summer Evening on Skagen's South Beach (Skagen Museum, Jutland), the creation of which I’ve written about in a previous blogpost. Lot 22 was first acquired by Queen Margarita of Italy - who also incidentally lent her name to the now arguably more famous eponymous pizza - since when the painting has descended through the house of Savoy until being acquired earlier this year by a private collector.

Peder Severin Krøyer’s Anna Ancher and Marie Krøyer on the Beach at Skagen. Estimate: £150,000–250,000.

But 'by direct descent' is arguably even more prized than royal lineage, and there are few provenances more distinguished than lot 4 in our sale, a lusciously mysterious landscape by Gustave Courbet. The first owner of this was Prosper Teste, Mayor of Ornans. Close friends with the painter, Courbet featured Teste in the centre of his extraordinary frieze of Ornans' characters Burial at Ornans (Musee d'Orsay). Since then the work has descended through four generations of the mayor's family.

Gusstave Courbet’s Le Ruisseau De Plaisir-Fontaine, Dans La Vallee Du Puits Noir. Estimate: £200,000 - 300,000.

Preserved in its original condition, the canvas unlined, the musky verdure of the valley of the Puits Noir is almost palpable as one stands before this extraordinarily enigmatic study of nature, its intense power released from La france profonde for the very first time.