I was reading Ecology, the Ascendent Perspective by Robert Ulanowicz when I came across the following interesting passage which made me think of this thread:

In January 1684 Sir Christopher Wren and Edmund Halley met with Hooke in Oxford during a session of the Royal Society. Wren and Halley were both interested in establishing a rigorous connection between the inverse-square law of attraction and the elliptical shape of planetary orbits. When they inquired of Hooke whether such a connection was possible, Hooke told them he had already completed the demonstration but that he intended to keep the proof secret until others, by failing to solve the problem, had learned to value it (Westfall 1983).

Wren and Halley evidently were dissatisfied with Hooke's coyness, for in August of the same year, when Halley was in Cambridge, he sought out Newton in order to pose the problem to Hooke's rival. Newton told Halley that he too had already solved the problem but had mislaid the proof...Wren decided to call the bluff of the two enemies by publicly offering an antique book worth forty shillings as a prize to the individual who could provide him a proof within two months.

Newton was distraught when Halley told him of Hooke's claim to a proof. Apparently, Newton did not lie when he claimed that he had already proved the connection, for a copy of a proof that antedates Halley's visit has indeed been found among Newton's papers. Being cautious in the company of someone who communicated with Hooke, Newton probably feigned having misplaced the proof. We can only imagine his horror, then, when he looked up his demonstration only to discover that it was deeply flawed. The thought of leaving the field open to Hooke drove Newton to near-panic. He abandoned all other ongoing projects to rush into seclusion and attempt a rigorous exposition. Once thus engaged, the positive rewards of the creative process seem to have drawn him ever deeper into the project. He virtually disappeared from society until the spring of 1686, at which time he emerged, on the brink of mental and physical exhaustion, with three completed volumes of the Principia in hand.

I'm worried about the lack of a citation for the last paragraph, but if this is accurate then it is very interesting.