In 1962 a mathematics professor named Edward O. Thorp published ‘Beat the Dealer’, the first book to mathematically prove that the house advantage in Blackjack could be overturned by card counting. That book, published over 50 years ago, laid the groundwork for thousands of counters to try their luck against famously hard-nosed casino security.

What Thorp proved using computer simulations, statistics and not a little of his own research was something that many gamblers had known for some time - that when the deck is rich is high values cards like 10s and aces players would win more often. In Blackjack dealers shuffle multiple decks together in a shoe, only shuffling again when almost all those cards have been dealt. Thorp’s revolutionary method only required that players keep track of the dealt cards, assign each a value and keep a running count.

Being a successful card counter doesn’t necessarily involve guile, deceit, disguises or the IQ of a Chess Grandmaster. In fact simple counting methods like the Ace/Five count can be learned in ten minutes, although successful application requires attention to detail and quick mental arithmetic. The only information required to keep a count is which cards have been dealt - which is obviously a very central part of Blackjack (i.e. a casino couldn’t stop a player keeping a count without drastically changing the rules).

Imagine the situation where a person with an eidetic memory walked into a casino. Such a person would have complete recollection of every card they had seen dealt that evening and, for them, tracking the count would be no more difficult than reading the value of a face up card is for you or I. If this player noticed, without any training, that a deck rich in 10s and Aces was better for the player, and bet accordingly, would he be considered a card counter, and could a casino rightfully kick him out?

The counter argument to the ‘public information’ argument is that casinos are profit making businesses which sell an entertainment product which is clearly marketed as a losing enterprise for the player. Casinos are private companies with a profit motive and, ultimately, complete control over whom they choose to admit. Just as a restaurant owner might exclude a professional speed eater from an all you can eat promotion a casino is entitled to exclude a professional card counter, and for the same reason - that customer is a loss making enterprise.

Many casinos have reacted to the threat of card counters by changing their house rules for Blackjack. Amendments like increasing the number of decks, or changing doubling and splitting rules, make it harder for counters to ever find a positive edge but it also means recreational players lose more.

Card counting is not the only form of advantage play casinos have to be wary of. In 2012 poker legend Phil Ivey began a 2 year court battle attempting to secure £7.3m he won playing Punto Banco at Crockfords casino in London. The problem was that he had done so by edge sorting, gauging small imperfections in face down cards to identify them, which put the odds hugely in his favour. It emerged Ivey, and a colleague, had requested a private high stakes table, and had requested the dealer move and rotate cards, presumably to make identification easier. Unlike card counting, which relies on public information, Ivey needed to know that Crockford’s cards had been made by a specific manufacturer with known, but miniscule, mistakes. He also acted deceptively towards the dealer, lying about his motives for wanting cards moved.

Almost all courts to have heard a case on card counting have declared it legal - meaning casinos cannot withhold counters’ winnings even if they are kicked out. Ivey was treated differently because he exploited a weakness the casino could not reasonably have been prepared for, and his legerdemain in doing so. These seem to be crucial legal litmus tests of whether an advantage play is fair game’ tests which edge sorting fails and card counting passes.

By shuffling the deck after every hand of Blackjack, casinos could forever rid themselves of card counters. The fact that casinos could, but haven’t, taken this step suggests that card counting is not a major concern. For every successful counter, or team of counters, there are likely to be dozens of wannabes without the knowledge or patience to make money and hundreds of regulars who neither know nor care what card counting is. Legally and morally card counters are not cheats, but it is hard to argue casinos should be legally obliged to admit them. It seems the great game of cat and mouse between counters and security has a while left to run.