People ride a prototype of a driverless vehicle as it is moves through a pedestrian area in Greenwich, east London, February 11, 2015. Britain has begun testing driverless cars in four cities, launching the first official trials ahead of a series of planned rule reviews to accommodate the new technology. (Photo by Suzanne Plunkett/Reuters)

Actors wearing masks of Syrian President Bashar al-Assad and Russian Prime Minister Vladimir Putin perform with body bags during a demonstration outside United Nations headquarters on January 24, 2011 in New York City. Protesters called on the U.N. Security Council to pass a resolution to attempt to halt al-Assad's crackdown on the Syrian uprising. (Photo by Mario Tama/Getty Images)

“Photographer Seth Casteel has definitely taken animal photography to new heights – or depths – with his hilarious photos of dogs chasing balls underwater. Casteel, who, naturally, has two dogs of his own (a mini Labradoodle and a Norwich terrier), said that he's drawn to underwater dog photography because the photos show a side of dogs that people may have never seen before”.

Photo: Seth Casteel Underwater Dog Pictures (Photo by Seth Casteel)

Mike “The Bedfordshire Bull Botteley” (left) takes on Chris “The General” Levy during a Chessboxing bout at the Scala nightclub on March 10, 2012 in London, England. A new hybrid sport combining chess and boxing in alternate 3 minute rounds, the winner is the one who knocks out or checkmates their opponent first. (Photo by Matthew Lloyd/Getty Images)

A deserted alley in the ghost town of Apice, in the province of Benevento, southern Italy, 22 November 2016. After the Irpinia earthquake that took place in southern Italy on 23 November 1980, leaving at least 2,500 people dead, 8,000 injured and 250,000 homeless, the town in the heart of the Sannio area was evacuated and its residents moved into what has become the new Apice. Only recently the narrow streets and the tragically abandoned buildings have started, slowly, to repopulate. (Photo by Cesare Abbate/EPA)

A woman is cooled down with a watering can as she sunbathes using insulating tape, at a beauty center in Belo Horizonte, Brazil, on December 21, 2017. Brazilian women take advantage of the beginning of the summer to sunbathe using the new national trend: natural tanning with insulating tape. Instead of using tiny bikinis on the beach, women avoid being bothered or stalked by getting taped in the shape of them, and lay in the sun over rooftops to enjoy the morning sun and get the perfect “marquinha” tan lines. (Photo by Douglas Magno/AFP Photo)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.