It isn't all that long ago since Manchester United was worth more than £1 billion sterling (€1.6 billion) on the stock market.

But that was back in the good old days when the market had fallen for the doubtful lure of football stocks.

Man Utd's arrival on the stock market led to a flood of other football flotations, from the likes of Celtic to, ahem, less glittering homes of football such as Millwall, Leicester City and Heart of Midlothian.

Now, the market has truly fallen out of love with the quoted football sector, with even blue-chip football stocks like Man Utd and Celtic trading at near historic lows.

Investors aren't keen on the lack of future earnings visibility that football clubs offer - all it would take for Man Utd's shares to go through the floor would be for David Beckham to break a leg. Strike threats from £60,000-a- week footballers and ballooning player salaries do not reassure investors, whatever about the enormous amounts of money teams such as Man Utd generate from their merchandise sales.

And so, even though they are sitting on a £6 million loss on their initial foray into Man Utd shares, JP McManus and John Magnier were back in the market last week taking their stake in the plc to just under 9 per cent.

The duo are second only to BSkyB on the Man Utd shareholder list and their stakebuilding has led to serious speculation that they are ultimately planning to take the plc private.

Seymour Pierce analyst Ms Catherine Bond said: "There appears to be credibility in the rumour that JP McManus and John Magnier have been looking at taking Manchester United private."

Man Utd is currently worth £310 million, but it is reasonable to assume that, given the strength of the brand (let alone the team's stranglehold on English football), any buyer would probably have to pony up to £500 million to take Man Utd private.

It's questionable whether normal earnings multiples can be applied to plc's like Man Utd. But, even at their current depressed levels, Man Utd shares are trading at more than 20 times last year's earnings.

Paying £500 million would mean paying more than 30 times earnings for a company whose assets can, in effect, walk out the door post-Bosman and whose future earnings are tied directly to success on the pitch as much as in the superstore.

Given their enormous wealth, few doubt that Messrs McManus and Magnier are capable of putting together a financial package to take Man Utd private.

The big question is whether their passion for football is greater than their passion for a financial return.