A well-known TV series hinted some time ago that Isaac Newton burnt the only known picture of Robert Hooke.
Is it true?
The question is whether there ever existed a portrait of Hooke. There is very little evidence to support this:
1) Hooke mentions a certain 'Mr Bonust' in his diary. In an entry for 16 October 1674 he wrote
'At Garaways. Left off taking tobacco — Mr Bonust drew picture.'
The name might refer to a certain Mr Bownest. However, if he did draw Hooke’s picture in 1674, this is the only reference Hooke made to it.
2) The only person who ever mentioned a portrait was Zacharias von Uffenbach, who visited the Royal Society in 1710. He was probably mistaken though, as no-one else made any reference to a portrait. Perhaps von Uffenbach had misheard the name 'Haak':
James Yonge, who visited the Society in November 1702 and was elected FRS at the time, recorded seeing ‘divers original pictures’ in the Council Room. He listed eleven portraits, including those of Robert Boyle and Theodore Haak, but Hooke’s was not among them. It seems unlikely that Yonge would have overlooked Hooke’s picture if it was there. Hooke was Yonge’s first contact at the Society: the two men had corresponded for many years and Yonge referred to Hooke in his journal as ‘my old friend’.
Neither Hooke's first biographer, Richard Waller, nor his posthumous editor, William Derham, mentioned the existence of a portrait either.
I can partially confirm this by the following evidence.
First. No portrait of Hooke survived. Unlike the portraits of many other members of the Royal Society of that day. (You can check this with Wikipedia). Second. This story is told by V. Arnold in his very popular book: Huygens and Barrow, Newton and Hooke. I have to say that Arnold is not always a reliable source of historical data, and he does not cite any references, and his other statements (mainly about ancient science) were widely criticized. However I have never seen this statement criticized. Third. It is known that Newton refused to be the President of the Royal Society while Hooke was a secretary. He accepted this position after Hooke's death.
But of course, it would be nice to have a direct contemporary account of this.
Here is another reference: http://melpor.hubpages.com/hub/The-Rivalry-Between-Isaac-Newton-and-Robert-Hooke . But again, it does not refer to primary sources.
I can only support "indirectly" Alexandre's answer; see :
No portrait is known to exist of Hooke
and the footnote n°24 [page 10] :
It has been suggested that in view of his unprepossessing appearance, Hooke may have been reluctant to sit for a portrait. He does not seem, however, to have had much vanity, and there is little doubt that the Society did have a portrait. When Zacharias von Uffenbach visited the Society in 1710, he reported seeing portraits of “Boyle and Hoock.” (‘Espinasse, 1956, p. 13; Chapman, 1996). Although Jardine ([Lisa Jardine, The Curious Life of Robert Hooke : The Man Who Measured London,] 2004) has claimed the discovery of a portrait of Hooke in London’s Natural History Museum, previously thought to be of John Ray, it now seems that the portrait is of Jan Baptist van Helmont.
Newton's animosity against Hooke is well known.
Having said that, I've difficulty to imagine that we ever know if he lost or stole or burned Hooke's portrait owned by the Royal Society...
On this issue, it seems to me that Wiki's entry dedicated to Robert Hooke is quite reliable (and detailed).