Street artist, who famously feuded with Banksy in a series of tit-for-tat overpaintings, fails to recover from three-year coma

King Robbo, a pioneering British graffiti artist best known for a long-running dispute with his more famous peer, Banksy, has died after three years in a coma following an unexplained head injury, a spokesman has said.

Robbo, who like Banksy kept his real identity a secret, was at the vanguard of the 1980s graffiti movement, known particularly for covering trains with his distinctive, US-inspired lettering.

In April 2011 he was found on a London street with serious head injuries and placed in an induced coma, never regaining consciousness.

A statement on his official Team Robbo website said: "It's with very great sadness that we have to announce that King Robbo passed away on 31 July 2014, due to health complications." It added: Team Robbo – 'All the way' – Robbo changed the art world … forever!"

It was never known how he suffered the injuries, though one theory is that he might have fallen down some stairs.

While influential enough for his work to be featured in exhibitions, and for the artist to receive a series of international commissions, Robbo's main celebrity outside the graffiti world arose more than 10 years after he retired from street art through a very public feud with Banksy, the Bristol stencil artist whose works sell for hundreds of thousands of pounds.

In an interview shortly before the head injury, Robbo said the disagreement began when he was introduced to Banksy at a party in the late-90s and the latter claimed to have not heard of him, something the older artist thought unlikely in the close-knit world of graffiti. The imposing 6ft 8in Robbo, who responded with a slap, said: "I gave him a backhander. It stunned him and knocked his glasses off his face."

Shortly after Robbo recounted the altercation in a 2009 book on graffiti, Banksy seemingly took matters into his own hands, partly painting over one of the then-last surviving Robbo works, on a wall by a canal in Camden, north London, accessible only by boat. Banksy added a stencil of a workman wallpapering over most of Robbo's letters.

Robbo abandoned his retirement to amend the work again, so the workman seemed to be painting "King Robbo" in large letters. The spat then got even more juvenile, with the letters "Fuc" appearing in front of "King".

The dispute spread to Banksy's own works, some of which were targeted by Robbo or his supporters. A north London stencil showing a hitchhiker with a sign saying, "Anywhere" was amended to say, "Going Nowhere", while another London piece showing children hoisting a Tesco bag on a flagpole said "HRH King Robbo".

In his 2011 interview, Robbo confirmed the feud was genuine: "I never wanted to take Banksy's stuff out, I just wanted to do something tongue in cheek. But when he put those three letters 'Fuc' up, that changed things."

The dispute was chronicled in a Channel 4 documentary filmed shortly before Robbo's head injury.

Banksy publicly objected to the programme, Graffiti Wars, saying it inferred he might have had something to do with his rival's accident. Channel 4 denied the documentary implied this.

Later in 2011 new artwork appeared on the by-now black-painted canalside wall where the original Robbo graffiti used to be, bearing the artist's name and a crown emblem, which many assumed was painted by Banksy as a tribute.