Riding as an amateur under the pseudonym "Angel Jacobs," Monserrate rode five winners this year in Britain, holding forth in the winners' enclosure after every triumph with a stream of highly quotable anecdotes. There was the story of how he got his name - the nurses in the hospital where he was taken as a tiny orphan thought he looked angelic - and of how he braided shoelaces to make a bit for his first pony during his poverty- stricken childhood in Puerto Rico. The great American jockey Angel Cordero Jnr, so he said, was his godfather.
But the talking stopped yesterday, when Jacobs was warned off by the Jockey Club. Barely a word passed his lips as he marched out of Portman Square in London, bringing to an end one of the most bizarre stories that even the turf has produced in recent years.
Just three months ago, Jacobs was the country's leading amateur jockey on the Flat, with a polished, professional riding style which shone like a beacon amid the unsteady labouring of his fellow part-timers. To the trainers who employed him, and the punters who backed him, it seemed too good to be true. And of course, it was.
After a little rummaging at the headquarters of the British Amateur Jockeys' Association, and a call to its equivalent in America, it was discovered that Jacobs was, in fact, Monserrate. He had been a professional jockey for several years in the United States, until he was banned in 1995 for failing a drugs test. He had then ridden as an amateur using the name Carlos Castro, which he borrowed from a famous marathon runner, until he was recognised by a former employer and the police were informed. Monserrate had been arrested after riding a winner at Aqueduct in New York, and led from the course in handcuffs to face charges of criminal trespass, tampering with a sporting event and forgery.
When the deception was uncovered, Monserrate's licence was immediately suspended, but formal punishment was delayed until yesterday. "Of course I regret what I did, but all I wanted to do was ride horses," was as much as Monserrate would say as he left the hearing. A little while earlier, he had admitted making a false statement when applying for his amateur rider's licence. This was probably wise given that Perry Mason and Petrocelli between them would have struggled to prove his innocence.
As a result of his offence, he will not only be banned from riding racehorses, but also from any employment in a racing yard, including those which train point-to-pointers. Nor will he be able to attend any racecourse, either in Britain or, in theory at least, anywhere in the world. It is up to the racing authorities elsewhere to enforce his ban, however.
Since horses are the only living he knows, Monserrate will be much the poorer as a result of his warning off. The same is not necessarily true of British racing, though. The five "winners" he rode during his brief spell on our tracks have been disqualified, but the owners of the horses involved were allowed to keep their prize money. A total of pounds 15,704.43 in extra prizes was paid to the owners of the runners-up.
A few shrewd punters, meanwhile, quickly realised that Monserrate was so far removed from the usual breed of keen but hopeless amateur riders that he was a little like a cashpoint machine on two legs. His first two winners were 4-1 chances, so in the betting shops at least, there may be fond memories of the little man from Puerto Rico who was not all that he seemed.