Bartoli looked at me. 'Lord Ravenscliff must have encountered tens of thousands of people. He travelled incessantly, throughout Europe, the Empire and to the Americas.'

'Look,' I said patiently. 'I am meant to write a biography which people will want to read. I am going to need personal details. How did he start? Who were his friends and family? What is it like travelling around the world? This is the sort of thing people are interested in. Not how much money he made in one year or the next. No one cares about that.'

He annoyed me; he treated me with neither seriousness nor consideration. I have never liked being treated like that. My colleagues believe I am overly sensitive to slights, real or imagined. Perhaps so, but it is a tendency which has served me well over the years. Dislike and resentment are great stimulants. Bartoli had converted me from someone who thought solely about the amount of money he was paid into someone who would have been determined to do the job properly even if he hadn't been paid at all.

I emerged from the office thinking it was time to start work, and there was one obvious place to begin. Seyd & Co was, by the standards of the City of London, a venerable institution. It had begun near half a century before to report on the credit-worthiness of traders wishing to borrow money from banks, and its investigations had gradually come to cover all aspects of finance. The more complex business became, the more obscure the origins of merchants, the greater the possibilities for duplicity and deception. And the more opportunities for companies like Seyd's to make money by shining light into the murkier recesses of man's greed.

For the most part – and officially – their business was to produce guides. The Birmingham Commercial List. California and Its Resources. All of which had to be bought by importers and exporters, dealers and merchants to avoid imposition by scoundrels. But very quietly and discreetly they did much more than that. By its nature, the City was full of rogues and thieves. But thieves have their codes of honour, and Seyd's winkled out those who did not follow the rules. Those who claimed financial backers who did not exist, who forgot to mention convictions for fraud in far-off countries. Who mentioned their assets, but not their debts. Whose word, in other words, was not their bond.

Once upon a time a company like Seyd was not necessary, for the city of money was a small place, and everyone knew their clients. Life was simple when bankers only accepted people they had dined with. They dealt with gentlemen, and there was nothing easier to know about than the extent of a gentleman's estate, or the solvency of his family. Now it is a gibbering Babel of unknowns. Is a man a penniless scoundrel or really one of the richest men in the Habsburg Empire? Does he really have a lucrative contract in Buenos Aires, or in reality should he be in gaol for having run from his creditors? How can one tell? Dissimulation is the first trick of banker and conman alike.

Seyd's discovered the truth. Not always, and not perfectly, but better than anyone else. I knew because I had on occasion done some work for them. I had been approached a few years previously to discover something of a man who was setting up as a company promoter in the north of England. He claimed to be able to bring seven cotton producers together to combine into one larger unit that could then be offered for sale. All he needed was some capital . . .

I had to take a day off work to travel north, but I got the truth out soon enough. Ernest Mason left the country a day before he could be arrested for fraud, but only because I tipped him off. He offered me money in return, but my conscience rebelled at being paid thrice for the same work. Once by my newspaper, as I wrote up the story of the fraudulent promotions, once by Seyd, who paid me for my report, and once by Mason. But undoubtedly many in the company's employ do so profit from their knowledge, and do worse. There is good money to be had in the City of London for those who really want it.

Wilf Cornford was too lazy ever to become rich. Had he possessed easy wealth by inheritance he would have been a scientist working out the various species and subspecies of the insect world. Instead, he catalogued the character and follies of homo economicus; it was his duty and his pleasure, and he was one of the few men I have ever met who could be considered truly happy. He could have been a power in the land, for all would have been afraid of him had they truly appreciated how much he knew. But he could not be bothered and, so he told me once, it would spoil his observations. All those people who gave him such an interesting time with their activities would begin to behave differently if they knew they were being watched.

It was he who first had the idea of hiring me for the occasional bit of investigation down in the police courts, and payment was occasionally some money, and more often a useful tip about a forthcoming arrest or scandal which his network of blabbermouths had passed on to him. On several occasions he had suggested I come to work for Seyd's properly, but I had never taken him up. I liked a more varied diet.

'Matthew,' he said in his even fashion when I knocked on his door and was admitted. 'Nice to see you again. We haven't seen you here for a long time.'

Wilf's way of speaking was as anonymous as his appearance. He was a portly fellow in his fifties, but not excessively so. He spoke with a measured neutrality, neither sounding like a toff, nor yet betraying any trace of his West Country origins, for his father had been a labourer in Dorset, and he had been sent as a child to serve in the house of the local gentry. There he had somehow learned to read and write, and when the family had brought him to London for the season some thirty-five years ago he had walked out one morning and never gone back. He found a job at a tallow chandler's writing up the books, for he had a fine script. Then he moved on to a corn broker, then a discount house, and finally to Seyd's.

'I was busy with the Mornington Crescent trial.'

He wrinkled his nose in disapproval. As well he might. This had not been a classic in the annals of British crime, and the only interesting aspect of the case had been the sheer stupidity of William Goulding, the murderer, who had kept the head of his unfortunate victim in a box under his bed, so when the police came calling – as they were bound to do, for the woman had lived in his house – even they could not have failed to notice the smell and the pool of dried blood which had dripped through the floorboards from the bedroom above and stained the parlour carpet. Goulding had not read the penny press, and so was possibly the only person left in England who did not know about the wonders of fingerprints for identifying even headless corpses. It was an open-and-shut case, but the trial took place in an otherwise quiet period, and the public does love its gore.

'I really don't know how you do your job,' he said. 'I would find it very dull.'

'In comparison to the account books you like to read?'

'Oh, yes. They are fascinating. If you know how to read them.'

'Which I don't. And that is one of the reasons I am here.'

'I was rather hoping you had come to give me information, not ask for it.'

'Do you know of a man called Ravenscliff?'

He stared at me for a minute, then very uncharacteristically leant back and laughed out loud. 'Well,' he said indulgently, 'yes. Yes, I think I can say I have heard of him.'

'I need to find out about him.'

'How many years do you have at your disposal?' He paused, and looked rather patronisingly at me. 'You could spend the rest of your life learning about him, and still never find out everything. Where are you starting from? How much do you know already?'