A series of sketches by artists such as Leonardo Da Vinci, Rubens and Rembrandt are set to be unveiled to the public for the first time in decades.

Described by experts as “art history as time travel”, the drawings capture “fleeting moments” of the artists’ surroundings with sitters ranging from their own pupils and everyday workers to royal employees.

The selection of around 50 portraits from the 14th and 15th centuries includes a series of works lent by the Queen’s Royal Collection.

Also featuring pieces by Durer and eight works by Holbein, The Encounter: Drawings From Leonardo To Rembrandt, will open at London’s National Portrait Gallery in July.

At a briefing on Thursday ahead of the exhibition’s opening, curator Dr Tarnya Cooper said: “We are looking at a period of extraordinary creativity when drawings proved an engine of the Renaissance and artists investigated the face to look into the human condition.

“The extreme precision of the drawings shows a moment of energy and connection between the sitter and the artist.”

Drawn in chalk, ink and metalpoint, the pictures mark the development of the European paper industry in the 15th century, providing an easily accessible medium for artists to practise “quintessential” skills.

Ink of paper studies by Rembrandt.Ink of paper studies by Rembrandt (National Portrait Gallery/PA)

While some were used as studies for the artists’ more well-known paintings, others such as Carlo Dolci’s shoemaker (c. 1630) were believed to have been intended as gifts or as payments for services.

Dr Cooper said: “Drawings gave artists the opportunity to draw whoever and whenever they wanted, without having to pay for professional sitters.”

Describing the fragile pictures as “extraordinary survivals”, she added that sketches were so undervalued by the artists that they often used them to “clean out pans”.

The Encounter: Drawings From Leonardo To Rembrandt will run from July 13 to October 22 at the National Portrait Gallery, featuring works from a range of British collections.