When a distraught-looking Indian-origin scientist was arrested in the New Year for the suspected murder of his famous Oxford colleague in an English village, the case seemed to have the makings of a classic murder mystery.

Now, Dr Devinder Sivia, an ex-NASA scientist, has been cleared of murdering his longtime friend and associate Prof Steven Rawlings, an internationally acclaimed astrophysicist, in a case of "accidental death."

Rawlings died on the night of January 11 at Sivia's home in Southmoor village. An inquest heard this week that Rawlings had been mentally ill for a year and died as Sivia defended himself during a violent psychotic attack.

Rawlings' final words were: "goodbye cruel world." But, in a surreal twist, Sivia thought he was playacting.

"This is a line from a Pink Floyd song, Goodbye Cruel World, from their album The Wall. I thought this might be a ploy to release him because it was so melodramatic," said Sivia, who came to Britain from India at the age of five.