Hotel staff practice self-defence skills after a training session given by team member of Special Weapons and Tactics (SWAT) team, in Hangzhou, Zhejiang province, April 7, 2016. (Photo by Reuters/Stringer)

A young arab boy, armed with a rifle and a knife, in the Aden Protectorate near Yemen. (Photo by Richards/Fox Photos/Getty Images). February 1938

Young Ian Archibald ponders the consequences of a complex critical study of beauty contestants during the Miss TV Times finals in London. (Photo by Central Press/Getty Images). 30 July 1971

Mosha, the elephant that was injured by a landmine, has her prosthetic leg attached at the Friends of the Asian Elephant Foundation in Lampang, Thailand, June 29, 2016. Mosha was 7 months old when she stepped on a land mine near Thailand’s border with Myanmar and lost a front leg. That was a decade ago... (Photo by Athit Perawongmetha/Reuters)

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.

Kim Kardashian goes shopping for gummy bears in sheer Gucci bra on October 9, 2017. She paired the risqué outfit with a waist-fitted midi length pencil skirt and clear lucite wedges from Kanye West’s fashion line. (Photo by Splash News and Pictures)

A labourer rides a donkey cart through a flooded street after heavy monsoon rains in Lahore on August 20, 2020. (Photo by Arif Ali/AFP Photo)

(L-R) Madelaine Petsch, Julia Fox, Kacey Musgraves, Kim Petras and Aquaria attend the Moschino Prefall 2020 Runway Show front row at New York Transit Museum on December 09, 2019 in Brooklyn City. (Photo by Astrid Stawiarz/Getty Images for Moschino)