They say that there is no such thing as a sure thing. However, the people that say this obviously aren’t aware of the betting anomaly known as arbitrage. In betting, arbitrages, often shortened to arbs, occur when two bookmakers have a difference of opinion, or one of them makes an error, and offer wildly different odds for the same event. Canny gamblers can then exploit this difference in the prices offered to place bets on all the possible results of a sporting event. For example, if one bookmaker were to offer 3-1 odds on England to qualify over Brazil in a knockout game, and another were to offer 3-1 odds on Brazil to qualify from the same game, a gambler would simply have to place both of these bets, with an equal stake, in order to guarantee a profit.
The same trick can sometimes be pulled in the world of spread betting, although it is getting more difficult than it used to be due to increased competitive monitoring. Here is an example of spread betting arbitrage. If we see a stock with a buy price of £100 and a sell price of £90, that has a buy price of £120 and a sell price of £110 with another spread betting firm, we can exploit this difference by selling at £110 with one firm and buying at £100 with the other, which means that we should make a profit no matter what happens.
Of course, spread betting firms go to great lengths to ensure that this does not happen very often, and are usually quick to correct their prices when it does. In order to be able to exploit spread betting arbitrage, you need to have accounts set up with several spread betting firms. This is because by the time you have registered with a spread betting firm in order to take advantage of an arb, they will probably have spotted it, and the opportunity will have passed you by. Spread betting firms may also, at their discretion, void arbitrage trades where allowed to do so by their terms and conditions.