Given the following context:

Head VI is an oil-on-canvas painting by the Irish-born figurative artist Francis Bacon, the last of six panels making up his "1949 Head" series. It shows a bust view of a single figure, modeled on Diego Velázquez's Portrait of Innocent X. Bacon applies forceful, expressive brush strokes, and places the figure within a glass cage structure, behind curtain-like drapery. This gives the effect of a man trapped and suffocated by his surroundings, screaming into an airless void.
Head VI was the first of Bacon's paintings to reference Velázquez, whose portrait of Pope Innocent X haunted him throughout his career and inspired his series of "screaming popes", a loose series of which there are around 45 surviving individual works. Head VI contains many motifs that were to reappear in Bacon's work. The hanging object, which may be a light switch or curtain tassel, can be found even in his late paintings. The geometric cage is a motif that appears as late as his 1985–86 masterpiece Study for a Self-Portrait—Triptych.
Head VI was first exhibited in November 1949 at the Hanover Gallery in London, in a showing organised by one of the artist's early champions, Erica Brausen. At the time, Bacon was a highly controversial but respected artist, best known for his 1944 Three Studies for Figures at the Base of a Crucifixion, which made him the enfant terrible of British art. Head VI drew a mixed reaction from art critics; John Russell, later Bacon's biographer, at the time dismissed it as a cross between "an alligator shorn of its jaws and an accountant in pince-nez who has come to a bad end". In 1989 Lawrence Gowing wrote that the "shock of the picture, when it was seen with a whole series of heads ... was indescribable. It was everything unpardonable. The paradoxical appearance at once of pastiche and iconoclasm was indeed one of Bacon's most original strokes." Art critic and curator David Sylvester described it as a seminal piece from Bacon's unusually productive 1949–50 period, and one of Bacon's finest popes.

answer the following question:

What is the first name of the person Russell was the biographer for? 

Francis