The programme for the event had been chosen by Gross himself, his son Tom revealed, and Humphries, for one, was stumped, well stymied.
After spouting Smith's four brief lines on the death of a German philosopher, he said that he'd give a box of Black Magic to anyone who could explain it to him. He glanced down at the front row, where sat Tomalin, Anthony Thwaite, Martin Amis and Christopher Ricks. Answer came there none.
Humphries then said that the critics had, quite rightly, given his last London show at the Haymarket, bad reviews. "Every critic gave me a stinker. John, too, gave me a stinker. But in a nice way."
A few actors joined the throng: Angharad Rees, Louise Gold (his niece), Peter Eyre, Nickolas Grace, joined by opera singer Jill Gomez and theatre critics Susannah Clapp, Georgina Brown, Charles Spencer, Patrick Carnegy, Robert Butler and Benedict Nightingale.
But theatre was a relatively small part of the Gross product: "the best read man in London" was a supreme man of letters on every serious publication going, including the Times Literary Supplement, which he edited.
This eminence was noted in speeches by Lord Weidenfeld and David Pryce-Jones, and in the presence of Antonia Fraser, Blake Morrison, Philip French, Victoria Glendinning (who read from a wonderful poem by Swinburne, "The Garden of Prosperine") and two of Gross' successors as TLS editor, Ferdinand Mount and Peter Stothard. It was right and fitting that the champagne reception was hosted by News International.
Amis languidly evoked Gross's diffidence and discretion and said that he'd never, before working with him on the New Statesman, encountered someone in whom brain power and self-effacement were so simultaneously apparent. He represented, he said, a pocket of discernment in the city, and gave some hilarious examples of his coaxing brilliance as an editor.
"Everything I write," concluded Amis, "I send by John's desk. I still do, and I always will."
Other recordings Gross had ordered up were Ella Fitzgerald singing Cole Porter's "What Is This Thing Called Love"; Kathleen Ferrier singing "The Keel Row"; "Oft in the Stilly Night" sung by the peerless Irish tenor Count John McCormack; and "Shenandoah" sung by Paul Robeson.
The absolute highlight, though, may have been Christopher Ricks reading a Robert Frost poem, "Provide, Provide" and giving a short masterclass in comic tone, gravity and phrasing all at once:
"No memory of having starred
Atones for later disregard,
Or keeps the end from being hard.
Better to go down dignified
With boughten friendship at your side
Than none at all. Provide, provide!"
John Gross had provided all right, but the friendship that flooded the RIBA had cost him nothing; everyone there just dug him in spades.