Mr Mohammadi embarked on the treacherous journey to Syria via Turkey after becoming concerned that his son was being influenced by jihadists.
With no British government representation in Syria to assist Britons who wish to return home, it is increasingly falling to members of their families to take on the responsibility. Earlier this month a 19-year-old Dutch girl who had travelled to Syria to marry a terrorist was rescued by her mother.
An intelligence source with experience of the case said: "Parents know that the British Government is powerless to help them bring back their children. So we expect more parents will make the dangerous journey of tracking their children and attempt to bring them back home."
Mr Mohammadi, who is of Kurdish Iraqi origin, is understood to have been aided in his mission by sympathetic members of the local community who put him in touch with contacts in Turkey. They helped him cross the border into Syria where he was able to locate his son and convince him to return to the UK.
On his return Ahmed was arrested under Section 5 of the Terrorism Act, but he was not charged and was referred to the Government's de-radicalisation programme.
A growing number of young Britons who travelled to Syria, many with the intention of assisting in humanitarian work, are returning to Britain, creating a headache for the police and security services. Some families have complained that the threat of arrest and prosecution is putting even more off returning home. It is estimated that more than 500 Britons have travelled to the region, with some of those recruited by Isil fighters. While some have been killed, it is thought that around half may have returned and have been assessed by the security services.
Among the latest Britons believed to have travelled to Syria to join Isil are four members of one family. They include two brothers from Camden in north London and two of their cousins from the West Midlands. Scotland Yard began investigating after the families of Mejanul and Kamran Islam from Wednesbury reported them missing. It is thought they may have travelled to Turkey via Milan to avoid drawing attention to themselves.
It has been reported that the network of terrorists behind Jihadi John, the Isil fighter who is suspected of beheading two British and two American hostages, has been smashed. It is claimed security experts on both sides of the Atlantic have identified 12 friends and contacts who are in communication with the terrorist.
The suspects, some of whom were known to the security services, are understood to be based across the UK but with some in London and others in Dewsbury, West Yorks.
