"AS I LOOK BACK on my life on the Turf," wrote

the Hon. George Lambton in Men and Horses I Have Known, "I am astonished at how many men I have known that you could bet your life on their doing the right thing."

Looking back at Dick Francis' life as a writer of novels about the turf, one is astonished at the number of ingenious rascals he has created, men to whom doing the right thing is a milk-and-water occupation fit only for the easy marks on whom they prey.

If Dick Francis' heroes weren't such a clever and determined lot, the turf would long ago have been choked to death by the ingenious chicaneries which Francis invents, and then, in climaxes as slam-bang as a four-horse stretch drive, manages to thwart.

Banker is the 24th in the series which began with Dead Cert and has perhaps the most elaborate plot Francis has yet devised.

In the racing fiction of George Lambton's time, villainy was a simple business of keeping Silver Blaze from the starting post of the Wessex Cup, to which end, readers of the adventures of Sherlock Holmes will remember, the security system of Colonel Rose's stable was negated by putting powdered opium in the mutton curry of the watchman groom.

Banker is as far ahead of "Silver Blaze" in complication as Einstein's infinity is of the wide blue bowl which Ptolemy saw, while the acknowledgement at the book's beginning of the help rendered by a professor of pharmacology suggests the scientific distance.

Scholarship is not art, however, and like Conan Doyle before him, Francis shows his special knowledge as quickly as an illusionist flashing a coin before your eyes, then hurries on to the major magic of telling a good story.

Once, in a conversation with Francis, I pointed out that all his heroes seemed to suffer from some handicap, to be mutilated physically by a riding accident, spiritually by a traumatic childhood, or financially by some family fecklessness or a series of losses at the track.

Francis agreed that he always liked to give his protagonists crosses to carry but, since we were talking in front of a TV camera, and since Francis has the gentlemanly reserve which might be expected from one who rode races for the Royal Family, we didn't get very far about what it was in his background that led to this fondness for cripples--real, psychological or financial. Perhaps it was no more than the good narrator's knowledge that we root for the racer who starts three fences behind, but certainly it is a concept he abandons in this book.

Tim Ekaterin, the banker, is so successful a person that when someone asks, "You have no real conception of danger, do you?," he replies, "Nothing that has happened so far in my life has made me fear I might die. I think . . . I know it sounds silly . . . I am unconvinced of my own mortality."

This is the sort of thing that might be said by one described elsewhere in the story as "A child of light . . . everything brightens when people like you walk in," but it is also obviously hubris of the highest order and pretty strange stuff from a Dick Francis character, a member of that breed which seems always surprised by its successes.

Of course, the hubris is tested in a manner which wild horses--as it happens, a perfect image--could not draw from me here, and which you will discover as Banker turns into the stretch and really begins to run, but I suspect that the change in basic character which Tim Ekaterin illustrates may have something to do with changes deep inside his creator.

When Francis hung up his tack and took to writing, it was, at first, as a newspaper racing reporter. He was familiar to the knowledgeable as a first-rate steeplechase rider, and to the general public as the man under whom the Queen's horse had sprawled to the ground just short of the winning post in the Grand National.

When he took up fiction he probably did not aspire to more that the mantle of Nat Gould, a competent hack whose turf tales gave reading pleasure to men who'd grown too old for The Boy's Own Paper.

On good days when the words came as fast as hoofbeats Francis might have dreamed of equalling Edgar Wallace who dictated improbable racing novels in the morning then lost their profits in the afternoon by backing improbable horses.

For a long time, though, even after his books began to sell extensively, he seems to have thought of himself as a man on the fringe, like so many of his principal characters, hanging on and hoping even though the past didn't seem to suggest that hope was a very good bet.

Now that he has finished his second dozen and is, I'm sure, looking into some arcane business which can convincingly be brought into a racing plot, I like to think that Francis no longer thinks of himself as a jockey who writes, but simply as a writer, and a good one.

I doubt that the grave polite man I met, who looked in his well-worn but well-cut tweeds like all the Empire- savers of John Buchan, could ever, without gulping, think of himself as a child of light. Still, I do know that everything brightens when a new Dick Francis book walks in.