Is it appropriate to measure the greatness of a painter by the range of human feeling they elicit in the viewer or display on the canvas? Perhaps narrow and deep should be sufficient, picking at one feature of human existence over and over again, worrying relentlessly at a scab to burrow deeper to discover and uncover the real wound beneath the surface. The thought occurred to me walking around The National Portrait Gallery’s outstanding exhibition of Francis Bacon’s portraits, Francis Bacon: Human Presence.

Bacon understood despair and the awareness of futility. He knew something about the longing to accept and impose cruelty. Suffering, isolation, and pain are never far from the canvas. He detected such things in the artists and paintings he admired, in Velazquez, Picasso, and Van Gogh. He discovered over time his own language in paint to express such things. His greatness lies in that language. His reputation is growing all the time, eight decades after he made his first impact on the world, and his work reverberates even more powerfully now when so many experience the world as a threatening, ominous, and lonely place.

Where is the affection, tenderness, and love in Bacon’s world and work? An exhibition devoted to his portraits might reasonably be expected to be a useful starting point, perhaps in paintings of his friends (including Lucian Freud and Frank Auerbach) or lovers (Peter Lacy, George Dyer, and John Edwards). But Bacon’s grim inspection of the skull beneath the skin is abundant even here and the portraits are full of snarling, grimacing, and screaming faces, many of them distorted by injury and pain. Only in some of the later paintings, especially one of John Edwards, is some tenderness detectable. Did Bacon soften slightly in old age?

This was one of the most impressive and compelling exhibitions I have seen in recent years. An opportunity to see some really important pictures rarely on display (notably the double portrait of Freud and Auerbach which I had only see before in reproductions), and confirmation, if confirmation is needed, of what a great (and grim) artist Bacon was.