The National Crime Agency (NCA) has named 25 people on their most wanted list, accused of crimes including murder, rape and drug smuggling.
And officers believe that five of them could be in London. Here are their names and stories.
Jack Mayle, born in Croydon , is wanted on suspicion of the supply of MDMA, methylphenidate (a pharmaceutical drug) and diazepam.
He is alleged to have run a drugs line in south London and Surrey called Flavour Quest.
When he was charged he fled, the NCA said.
He is around 30-years=old, 5ft11in tall and has a muscular build.
Mayle has a number of distinctive tattoos including a diamond under his left eye, a tattoo reading ‘Croydon’ on his left forearm and left hand tattoo which says “money never sleeps”.
He is known to carry weapons; is a regular gym goer and vegan.
In his absence, John Barton was sentenced to 20 years imprisonment in 2003 for conspiring to import a commercial amount of heroin into the UK.
The crimes took place between 1999 and 2000 but he has never seen justice.
He is believed to have links to Fuengirola in Spain as well as London.
Barton is described as around 170cm tall, of medium build, with dyed receding hair.
Ersin Mustafa is a former employee of bank JP Morgan Cazenove who is suspected of insider dealing.
Between 2006 and 2008 he worked at the London branch where he allegedly obtained information about future acquisitions and mergers, which were provided to others who then traded using this information.
The group he is alleged to have been involved made approximately £2.5million.
He was arrested by City of London Police in 2008 and was released on bail.
But he has not been seen since and it is believed he fled the UK around December 2009.
The NCA believes he could be in London and he is described as being around 165cm tall, of stocky build with dark hair and tanned skin.
Daniel Dudic is suspected of being involved in a plot to import 255 kilos of cocaine into the country back in 2011.
A number of other individuals were convicted of the crime but Dudic was never caught.
Originally from Serbia, it is thought that Dudic could be in London.
The conspiracy involved a small UK vessel meeting a commercial container ship in the English Channel from which the drugs were transferred.
Although Dugic was not on board either vessel, he is alleged to have played a major part in organising the importation.
Christakis Philippou, aka Christakis Chrysostomou, is said to have been involved in a travel fraud scene.
Between 2004 and 2006 he and co-defendants are said to have repeatedly set out to acquire, or sometimes to set up from scratch, travel agency businesses which were used as vehicles for fraud.
The travel agencies attracted customers by offering cut-price holidays.
The prices were so low that legitimate companies could not compete with them. In each case, the travel agency ceased to trade, leaving around 20,000 customers without a holiday.
Philippou, who is believed to be in London, is described as being around 165cm tall, with grey receding hair and tan skin.