“Basically a mobile phone is akin to having a tracking device on you,” says Bleksley. “Even if location services are disabled the state has the means to track you.”

Timescale: minutes. “There has to be some communication between the mobile phone company and law enforcement,” says Bleksley. “But in a mission critical situation – life or death – the red tape is cut through and police are given that info in as close to real time as possible. “

Don’t: use bank cards

“You wouldn’t want to be using any kind of cards.” says Vlissidis. “Or your ApplyPay device unless you really want to get picked up quickly,” “If you have time to plan, gather quantities of cash.

Timescale: minutes. “If a bank card or account is flagged by us that account is monitored 24/7” says Bleksley. “The minute there is any activity the information is quickly passed to the police,” says Bleksley. “Systems have been honed over the years to ensure that information comes almost instantly. From there it’s a just question of how quickly officers on the ground can move.”

Do: torch your tablet, lay waste to your laptop, pulverise your PC

“Before you run try and eliminate your digital footprint, which is difficult,” says Vlissidis. “We can gain an extraordinary amount of information from accessing accounts, social media etc. If you planned your escape, it will be in your search engine history.” If you asked questions online, there will be a record. “Anyone who thinks that private chats on social networks are actually private is an idiot. Even if you deactivate your account, it disappears from public view but all the information is still there and generally the state has the ability to access it.”

Don’t: phone home

With police monitoring your family and friends, this is an instant giveaway. 93 percent of police requests to access phone calls or emails are granted. Last year they peaked at just below 250,000.

“This would be the most difficult thing for me,” says Bleksley, who himself spent two years in witness protection after a contract was put out on him. “Fugitives find it incredibly difficult to cut themselves off from friends, family, loved ones. The lure is incredibly strong.”

Don’t: check your emails

“Email is tremendously useful, says Vlissidis. “We can monitor accounts and the second you log on it will be flagged and we can tell immediately where you’re coming from by reversing the IP address.

Timescale: It’s only a matter of minutes generally speaking. If you’re using a wireless system it might take a little longer – but not much. You can use systems like Tor that’s designed to anonymise you but the truth is, if we’re sitting on your email and we see you log in, and you’re using, say, a mobile phone for access then there are ways for us to track it.”

Do: worry about CCTV

Britain has one CCTV camera for every 11 people. It is estimated that the average city dweller is caught on CCTV 70 times a day.

“The majority of city centre CCTV systems are owned by local authorities and operated by police employees,” says Bleksley. “The systems are very, very extensive. In some you can track people from the moment they enter a city.”

Timescale: “It’s simply a question of how quickly a human can impart that information to officers on the ground.” Although the likelihood of being identified by CCTV alone is small unless operators already know you are in the area, once your presence is flagged by other sources CCTV is the No 1 means for tracking you.

Don’t: worry about facial recognition technology

“It is one area of forensic science which is in its infancy,” says Bleksley, “but I’m sure in the years to come it will become prevalent.”

Do: travel by bus or train

As they take cash, but avoid station CCTV.

Don’t: use motorways

The Highways Agency operates an Automatic Number Plate Recognition (ANPR) camera systemwith around 8,000 cameras. On the major road networks you are never more than 15 miles away from an ANPR camera.

Timescale: “It’s a nationwide police resource and operates instantly,” says Bleksley. “There are also many private APNR systems, say, in supermarket car parks. In those the process can be a little lengthier because providers have to be brought on board.”

Do: disguise your physical appearance

“After technology, our best weapon is 100,000 pairs of eyes and ears on the ground – policemen plus the public who often are an enormous help. There’s also the massive media machine that the police are able to call upon.” So, delete any online photos. The less recognisable you are the better.

Do: plan ahead

Accumulate as much cash as you can in the weeks, preferably months, running up to departure. Plan your escape offline as much as possible. Prepare disguises, alternative identities. Share your plans with no one, unless it is to arrange communication channels. “The longer you’ve got before you run the better chance you have,” says Vlissidis. But stay away from tech. Roll the clocks back 15 years and pretend the internet doesn’t exist. If you have to devise a strategy for communicating with loved ones keep it old school – intermediaries, dead letter drops, proper spooks stuff.”

Don’t: assume rural is remote

You’ll stand out like a sore thumb in small communities, and sleeping rough/living wild is hard to keep up for any amount of time even if you’re trained. “I don’t think staying off grid necessarily means the back of beyond,” says Vlissidis. “That would be difficult for an extended period of time. I’d probably look at lower grade accommodation, things like hostels, B&B’s that take cash – old school basically.

Do: be strong

We all lay down patterns that can expose us, but the sheer psychological slog of keeping up the mask is tough. Maintaining an assumed identity can mess with your head too. “Living the adopted life of a completely different person in a strange environment, dreading leaving my front door, having to layer lie upon lie upon lie,” as Bleksley describes it. Longer term, this is the thing that will get you caught.

Don’t: whatever you do, challenge people to find you

In 2009 Wired magazine offered a bounty of $5,000 to anyone who could locate journalist Evan Ratiff during his attempt to vanish for 28 days. The internet community’s response was extraordinary, as was his story – a cautionary tale for any wannabe fugitive.