Writing to Miss Olga von Glehn from Villa Congreve (also), San Remo, on 10 March 1871, John Richard Green states:

I have just been seeing Lear’s pictures packed off for the Academy. I shall be home just in time for a visit to it with you ― do you remember our visit last year? One of the pictures hangs about me still, a quiet reach of the Nile all dead with evening, behind a fiery blaze of sunset, and in front of it the weird gigantic “wings” of a Nile boat ― dark olive green in colour. There was a strange wild creepiness about the picture, but I doubt whther it will get hung. Lear has “Academy Wednesdays” in the studio of his new house, which he has hung round with 100 of his water-colours from Egypt, Palestine, Montenegro, Greece, Italy, and the Riviera. His whole life seems to have been an artistic “Wanderjahr,” and perhaps it is owing to this that he has preserved such perfect freshness of feeling, his humour and gaiety, his love of children and nonsense. He is delighted just now with the sale of his Christmas book, some 3000 copies have gone, but his profits are only some £60! Still he is happy, and every dayy he comes in and chats and tells me of some new idea for a picture, or of some change in a picture we have seen. Surely nothing is so perfect, so self-sufficing as the artist-life. (Letters of John Richard Green, edited by Leslie Stephen. London: Macmillan, 1901, pp. 290-291. Available at archive.org.)

He continued the letter on 20 March:

Is it possible this letter can still be here, dear Olga, lurking in secret places, when I thought it resting next to your heart or buried under your pillow to woo sweet dreams? What a change since I began it ― Lear vanished and San Remo vanished, and around me instead of the soft circle of its olives the hard red line of the cliffs of Mentone! (Ibid. p. 291.)

In 1871 Lear had four paintings in the Royal Academy:

Cattaro in Dalmatia.
On the Nile near Assioot.
On the Nile, Nagadeh.
On the Nile near Ballas.
(Algernon Graves, The Royal Academy of Arts; a complete dictionary of contributors and their work from its foundation in 1769 to 1904. London: Henry Graves and Co., 1906, vol. V, p. 13.)

The one Green describes might be “On the Nile near Assioot,” perhaps the one sold at Bonhams in 2009, though I do not see “gigantic wings:”

John Richard Green, “the people’s historian,” should be the “reverend” Green which had an important part to play in the scandal of Walter Congreve’s relationship with a servant; on p. 212 we are told that

In 1870 he made his first journey in search of health, and spent the winter mainly at San Remo. The winter of 1871-72 was again spent at San Remo.

John Richard Green (1837–1883), by Frederick Sandys, 1882.

Though at the time he was writing his magnum opus (1869-1874) he should have had “scarcely a hold on life” and been “incessantly vexed by the suffering and exhaustion of constant illness, perplexed by questions as to the mere means of livelihood, thwarted and hindered by difficulties about books in the long winters abroad” (“Introduction” by his wife, Alice Stopford Green, to the first volume of his A Short History of the English People. London: Macmillan, 1902, p. xix) he seems to have had a very active part in Congreve’s affair, at least as it is told in Lear’s diary.

On hearing from Giorgio that Congreve was thinking of bringing back Ellen, the pregnant servant, and marrying her, Lear rushed to Villa Congreve “to see Green,” who, on hearing of this, “owns (& denies not) that E. ― was ‘far from’ unwilling to act in unison with himself or with Lambert” (Diary, 13 December 1871): which seems to mean she was available as a lover to other men.

Lear’s investigation into the affair came to an end on 13 February 1872 when Congreve told him what had really happened, according to Ellen:

Congreve sent a note by the boys ― “anxious to see me ― much cleared up” &c. ― so we were to meet at 4.30, & he came then. He began at once on the misery topic. He had said to E. on going there [Nice, where she was staying] ― “what is there between you & Mr. G. Tell me the truth.” & she said ― [“]O! ― how glad I am you ask! It is the only thing I have concealed from you; & I have never had moral courage to tell you.” ― Then she confessed that early last winter [i.e. 1870-1871] G[reen] had attacked her saying he saw plainly there was something between her & C[ongreve] ― & that he might also share the good. She resisted all this, ― but one night he came to her room, & preventing her alarming the house, lay down on her bed, & told her stories ― some of wh. are unique as ecclesiastical=libidinous. Being fearful of scandal she endured that more than once, getting however, more & more angry ― but as he came at 3 or 4 A.M. he surprised her asleep. One morning he used force, & nearly succeeded, ― but desisted on her violent resistance & commencement of alarming the house. After that, he did not touch or look at her. As the connexion between her & C. never took place till May ― (by day times ― when E. brought some broth to C. he being in bed & unwell,) ― all his inventions about her “details” are sheer lies: ― & not only this, but scores of lies are evident on the whole of his story. By his own account to E. ― he had women, great & lowly ― right & left: ― but he got her to promise silence on what he had done, by appealing to her pity as to if she would like to ruin his professional prospects. It is not possible to put down a 100th part of what C. told me; but I am well sure that G. is a bad fellow out & out.

The story is told in greater detail in Michael Montgomery’s biography (pp. 239-241); however, neither Montgomery nor Levi, the only ones to mention Green, connect the person to the historian: Montgomery even wrongly states that he was “the local Anglican vicar.”

The fact that Green had had “women, great & lowly” throws a shadow on his period as a curate in Stepney:

He served as curate at St Barnabas, Finsbury (1861–3), Holy Trinity, Hoxton (1863–4), and St Peter’s, Stepney (1864–5); in 1865 he was appointed incumbent of St Peter’s. In addition to his religious duties, Green undertook a gruelling regimen of social work among his parishioners, including the district’s many prostitutes.
Anthony Brundage, ‘Green, John Richard (1837–1883)’, Oxford Dictionary of National Biography, Oxford University Press, 2004 [http://0-www.oxforddnb.com/view/article/11391, accessed 14 Feb 2016]