Samba dancers outside Woolwich station celebrate the opening of the Elizabeth Line in London, England on May 23, 2022. Originally due to open in December 2018, the £18.8bn railway links Reading and Essex via central London. (Photo by Jill Mead/The Guardian)

A participant takes part in donkey racing, during the 21st edition of annual Lamu Cultural Festival, in Lamu, Kenya, Saturday December 2, 2023. (Photo by AP Photo/Stringer)

A person dressed as a zombie mermaid poses for a photo as she interacts with patrons at the Haunted Hotel Takeover Halloween party at hotel Ziggy in West Hollywood, California, U.S., October 29, 2022. (Photo by Mario Anzuoni/Reuters)

A soldier reacts after falling off a horse as members of the King's Troop, Royal Horse Artillery, arrive at Green Park for a gun salute celebrating the King's birthday in London on November 14, 2022. King Charles III is celebrating his first birthday as monarch as he turns 74. (Photo by Daniel Leal/AFP Photo)

A dog walks on the street as it snows in Kyoto on January 25, 2024. (Photo by Philip Fong/AFP Photo)

Reuters multi-award winning photographers are celebrated here in a three part retrospective on the 30th anniversary of the service's launch. They have captured dramatic images illustrating the human tragedy of natural disaster and war as well as the fallout of economic events across the continents, creating iconic images, recognised around the world. Here: an injured soccer fan is carried to safety by a friend after a wall collapsed during violence between fans before the European Cup final between Juventus and Liverpool at the Heysel stadium in Brussels, May 29, 1985. 39 people died, and a further 600 were injured. (Photo by Nick Didlick/Reuters)

Residents watch the ocean waves crash into the water front, after the passage of Hurricane Irma, in Cuba, Sunday, September 10, 2017. (Photo by Ramon Espinosa/AP 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.