London Briefing: There was only one topic of conversation last week in the City of London: the £50 million (€74.5 million) man.

In the bars, on the blogs and in an avalanche of envious e-mails, all the talk was of Driss Ben-Brahim, the hotshot head of proprietary trading at Goldman Sachs who is said to have received a £50 million bonus from his grateful employer.

The 42-year old Moroccan-born trader was keeping a low profile, despite being door-stepped by reporters eager to ask him why he thought he was worth 20,000 times more than the average annual British wage.

His astonishing payout, together with more "modest" bonuses of between £1 million and £10 million for scores of his colleagues, is the culmination of a record-breaking year for the investment banking industry, and for Goldman Sachs in particular.

Last week, just before the bonuses were declared, Goldman Sachs reported its most profitable year ever, with a 69 per cent surge in earnings to a record $9.54 billion (€7.22 billion). Earnings in the final quarter all but doubled.

The investment bank said it will have paid out as much as $16.5 billion this year to its 26,500-strong workforce, around 5,000 of whom work in London.

No breakdown of the figures is given and Goldman's partners and traders are notoriously secretive about what they earn. But it is clear that the sums involved are of superstar proportions and are likely to push property prices even higher in the exclusive "bonus belt" area around Knightsbridge and Chelsea, and also in the home counties.

The widespread excitement about Ben-Brahim's bumper bonus package reignited the debate on whether anyone - footballer, film star or pop idol - can really be worth that much.

Sure, like the rest of his well-rewarded colleagues, he works long hours, but then so do junior doctors.

And there is, of course, another side to the City of London, one where bonuses play no part.

As Goldman staff enjoyed their Christmas party at The Collection, an exclusive Chelsea restaurant, the army of cleaners employed at the firm's London offices reported as usual for the night shift.

In the build-up to the bonus season, unions have targeted Goldman's London headquarters in Fleet Street for a series of protests about rates of pay.

Scuffles broke out recently when staff from a contract cleaning firm in which Goldmans has a stake stormed the foyer.

Brandishing "Goldman Sucks" placards, the cleaners are campaigning for an increase in their hourly rate of pay from £5.35, which is the national minimum wage, to £7.10, along with the right to paid sick leave.

Their hours are also long, perhaps even longer than some of the Goldman partners. But, whether it can be morally justified or not, the simple fact is that to Goldman Sachs, Ben-Brahim is worth every penny of his £50 million.

He will have earned many hundreds of millions for the firm last year, as he did the year before and the year before that. The payment is not just to reward him for past performance but also to ensure that he is not lured away by a rival waving an even larger cheque.

Shy billionaire

Another even wealthier man was also making the headlines in London last week. Mike Ashley, the billionaire owner of the Sports World chain, had never given an interview nor, apart from a grainy shot of him playing squash as a teenager, had his picture ever been published.

So low was the profile of the 42-year-old retail entrepreneur that few of his staff had any idea what he looked like.

Now, however, we all know. Last Friday, in a brief and rather bizarre conference call with financial reporters, Ashley broke cover to answer questions and also released the first photograph of himself in 25 years.

Although he had previously been dubbed the British Howard Hughes, the photo shows a jovial, ordinary-looking bloke with a figure that suggests his squash days are long gone.

The billionaire broke his lengthy silence amid growing speculation that he plans a stock market float for his retail empire, which also includes the Lillywhites sports store in Piccadilly and the Dunlop Slazenger, Lonsdale and Kangol brands.

Estimates of its value range from £1 billion to £2 billion, although Ashley refused to reveal any new figures last week. The last available results for the business showed profits of £74 million in the year to April 2005, on sales of just over £900 million.

He told of his ambitions to turn the 380-shop Sports World chain into a global brand and said he was targeting Europe for expansion.

He has also built a 29 per cent stake in Blacks Leisure, and may be planning a bid. That was another subject he declined to comment on in his brief chat with reporters last week. Mike Ashley may have come out of the shadows at long last but it looks as though he'll keep the City guessing for a while longer.

Fiona Walsh writes for the Guardian newspaper in London