His Royal Highness King George III is probably best known for two rather unfortunate things.

The first is that under his reign the British Empire lost America to independence. The second is that he went bonkers during his later years, what what.

And so to the 'Bond King' of the markets Bill Gross, a world-renowned and ageing American fund manager whose Pimco empire is dwindling and who has exhibited some perplexing behaviour in recent months.

George III suffered a number of manic outbursts while king because, it is believed, of a genetic medical condition called porphyria.

Gross, without the mania but with all the eccentricity, has himself had a number of bizarre explosions.

The latest of these came in his investment outlook for May, which included a peculiar description of the pleasure of sneezing.

"There's nothing like a good sneeze; maybe a hot shower or an ice cream sandwich, but no – nothing else even comes close," Gross wrote.

"A sneeze is, to be candid, sort of half erotic, a release of pressure that feels oh so good either before or just after the Achoo!

"The air, along with 100,000 germs, comes shooting out of your nose faster than a race car at the Indy 500."

Okay then, Bill. But the oddness doesn't stop here. Gross has been caught up in an acrimonious battle with his former protégé at Pimco, Mohamed El-Erian.

El-Erian quit as Pimco chief executive in a surprise departure from the asset management behemoth that Gross co-founded.

He had been lined up as Gross's heir, but behind the scenes jousting between the pair caused El-Erian to walk out.

A clash was exposed by the Wall Street Journal, which detailed a confrontation between the two in front of colleagues at Pimco's Californian HQ.

Gross boasted of his "41 years of investing excellence", before goading El-Erian with "what have you got?"

El-Erian reportedly responded by saying he was "tired of clearing up your s**t".

In a subsequent interview with Reuters, Gross accused El-Erian of "writing" the WSJ article and of trying to undermine him.

The Reuters reporter asked to see the evidence, which Gross claimed to have, that El-Erian was behind the WSJ report.

"You're on his side. Great, he's got you, too, wrapped around his charming right finger," Gross snapped back, before suggesting he had listened to El-Erian's calls.

A Pimco spokesman later told Reuters that Gross "categorically denies" listening to any calls and even making any of the comments reported in the article.

Underneath all of this is Pimco's crumbling empire. Weakening returns has led to billions of dollars of outflows from Pimco-managed funds.

In fact, the total is $55.2bn that has been withdrawn since April 2013 from the world's largest bond fund as the returns fall behind many of its competitors.

And it's all getting to Gross.

"It's been like a near-death experience, an emotional blow," he told Bloomberg Businessweek.

"Whenever I read the newspaper, I say to myself 'at least my wife loves me'."

So the Bond King's reign looks like it is coming to an end much like that of the Mad King of old, in a blaze of rantings and lost former subjects looking for prosperity in a New World.