There were, needless to say, concerns about the honesty of the sport, as reported in Vanity Fair in 1871:
We have seen the last of the practice of the eights, and almost as soon as this number of the FAIR sees publicity we shall have seen also the race and its result. We never remember a greater excitement than on the present occasion, and never such an infusion of the gambling element as is now unfortunately introduced as a leading feature in the entertainment. City speculators plunge as greedily on light and dark blue as on cotton or indigo; and having never seen either crew in their lives, nor having even succeeded in feathering a scull, gravely tell you that it is a “real good thing” this way or that; that they know on the “very best authority” that A and B in the Oxford boat can’t stay, or C and D of the Cantabs are lamentably over-trained. As for the “ring,” they quote the odds as formally as prices for the Chester Cup and Derby, and only lament that there is no such luck as a possibility of “squaring” it -- judging charitably University probity by their own.
This gambling is a serious evil; without raising the abstract question of morality, it puts University men on thorns, lest unscrupulous speculators, finding that they cannot buy or square the crews, should attempt to “nobble” them as a last resource. We more than suspect that this sort of game has been planned, though futilely, before now. We remember how in ‘67, when Oxford were hot favourites, ugly rumours came to our ears from private sources as to whereabouts in the course a boat was provided to run into Oxford, should they be leading. Forewarned, the presidents were forearmed, and though at the expected place a suspicious-looking craft shot erratically into the track, both boats were wide off shore, Cambridge the nearer of the two, and mischief, if intended, was averted. This year Cambridge are public favourites, and the ring are “fielding” at the odds. If any attack is planned, it will be against the light blue, but we sincerely trust that the guard of police at the boat-houses, and in police boats during the race, will suffice to overawe any such villainy.
In 1912 a Vanity Fair correspondent recalled that an American undergraduate at Cambridge opened a book on the boat racing, hoping to fleece the innocent English. During the course of the evening, every one of the crew of his own college boat, including the cox, approached him individually and privately to put half-a-crown against their own boat. As a result he became convinced they were going to throw the race and when the rest of the college swarmed round next day to place a sovereign each to win, he was happy to give five to one.
Of course, they romped home in record time and the amateur bookie faced a payout of £500 against an income of £1 2s 6d.Thanks to Wikipedia