Ever wondered how professional hitmen actually work? A new study from Birmingham City University has shed some light on the shady world of assassins in the UK. Shutterstock.com The British Hitman: 1974-2013, from the Howard Journal of Criminal Justice, analyses criminal justice data, interviews with people who know how assassins work, court testimony and newspaper coverage to build a picture of the kind of people who carry out murders for money.There are relatively very few contract killings in the UK, compared to other countries, but the ones that do happen are far removed from the Hollywood cliches of professional hitmen. 1. The study says the amount of money that changes hands is very small, "lower than what one would expect as compensation for efforts and risks of the hiree." Shutterstock.com The average cost of a "hit", the researchers say, is £15,180, with £100,000 being the biggest price they uncovered, from a 1994 killing. 2. The average age of a hitman in the UK is 38, but killers can be as young as 15. Shutterstock.com The youngest killer profiled in the study is Santre Sanchez Gayle, who was only 15 years old when he killed Gulistan Subasi in North London in March 2010. He got £200 for his trouble and spent it on a Dolce & Gabbana beanie hat.Gayle was sentenced to a minimum of 20 years in prison and the police considered the murder to be the work of a "professional". He was caught after his bragging about the crime prompted a friend to tell the police.The oldest killer the study could find was 63. 3. Tuesday is the most popular day of the week to carry out a hit. The researchers add that March, May and July were the most common months for a hit to take place, but they also caution that neither of these facts are statistically significant. 4. Most killings take place in ordinary towns and neighbourhoods - not smoky rooms or dark alleys. Shutterstock.com Chillingly, most of the hits studied by the researchers took place while the targets were walking the dog, going shopping or on their way to work. In many cases the killer lived in the same neighbourhood as the the victim. 5. Shooting is unsurprisingly the most popular method of killing people for money, but beating people to death is popular too. 6. There are four distinct types of UK assassin, ranging from the bumbling "novice" who always gets caught, to the elusive "master". Most hitmen are carrying out a hit for first time and there is precious little evidence or court testimony on the master category. But the researchers mention the killing of Frank McPhee in Glasgow, in May 2000, as a good example of a professional hit."McPhee, popularly described as a ‘gangland boss’, was killed by a single shot to the head from a .22 rifle with a telescopic sight outside his house in Guthrie Street, Maryhill – just 500 yards from the Maryhill Police Station," the study says."It was widely believed that McPhee was killed by a hitman to prevent him from becoming involved with the sale of drugs in Northern Ireland (Observer, 13 August 2000). McPhee's killer has never been brought to justice." 7. Hitmen are usually caught by leaving rather dumb clues behind. Shutterstock.com Police caught 63-year-old David Harrison in 2010 after mobile phone records placed him in the area where the shooting happened for three consecutive days prior to the hit. He also had £26,000 in banknotes dated within two weeks of the murder, plus he had cut out newspaper stories of the killing.Yet, he was still described in court as a "professional" hitman.