Born in Brussels in 1960, Jacques Billen founded his gallery in 1988 in Sablon, the antiques district of his home town. The gallery is called Harmakhis making reference to the Great Sphinx of Giza, assimilated since the New Kingdom to "Horus in the Horizon". In fact, before it went to join the collections of the Staatliches Museum Ägyptischer Kunst München, a sphinx with mane of Pharaoh Amenemhat III of the 12th dynasty (c. 1844-1797 BC) served as the emblem of the gallery for some time and welcomed visitors.

A graduate in History of Art and Archaeology and Oriental Philology and History of the Université Catholique de Louvain, Jacques Billen is first and foremost a specialist in ancient Egyptian art. Nevertheless, he also offers a nice selection of classical antiques and occasionally from the Middle East.

In parallel with his career as an antiquities dealer, Jacques Billen is also an expert in Egyptian art. As such, he provides valuable advice for a great number of collectors and institutions around the world, and also participates on various expert committees at several famous international fairs.

Jacques Billen is a member of the following expert and antiquarian associations: Chambre Belge des Experts en Oeuvres d'Art (Belgian Chamber of Art Experts) Chambre Royale des Antiquaires et des Négociants en Œuvres d'Art de Belgique (Royal Chamber of Belgian Antique and Fine Art Dealers), International Association of Dealers in Ancient Art (IADAA), Syndicat National des Antiquaires (SNA).

He has been involved or actively participates in the following antiques fairs: 

Ars Antiqua Brussels
La Biennale des Antiquaires
Brussels Art Square
Foire des Antiquaires de Belgique (Palais des Beaux-Arts)
Masterpiece London
Winter B Sablon