The role of a radical preacher has come under scrutiny after it emerged that at least three young men from Cardiff had travelled to fight with the Islamist group Isis in Syria and Iraq.
Saudi-born Mohammad al-Arefe was banned by the Home Office from returning to Britain in March 2014 after a series in sermons in Cardiff, Birmingham and London.
Nasser Muthana and Reyaad Khan, two Cardiff-schooled 20-year-olds who recently appeared in an Isis propaganda video, had advertised an al-Arefe talk in their city in April 2013.
Mr Muthana's 17-year-old brother is also thought to have travelled to the region.
ITV News has learned that al-Arefe spoke in the Welsh capital on at least two occasions in 2013.
A Home Office spokesperson said: “We can confirm Mohammad Al-Arefe has been excluded from the United Kingdom.
“The Government makes no apologies for refusing people access to the UK if we believe they represent a threat to our society.
"Coming here is a privilege that we refuse to extend to those who seek to subvert our shared values.”
A third young Briton who appeared alongside Muthana and Khan in the Isis video was today named as 20-year-old Raqib, known to have attended a mosque in Aberdeen.
It is believed that Raqib's family moved to Leicester in the last few years.
Ibrahim Alwawi, imam of the Aberdeen Mosque and Islamic Centre, told the BBC: "We, as the Muslim community in the city of Aberdeen, are shocked like everyone else.
"We are co-operating with the authorities as we usually do."
Today the Prime Minister warned of dangerous consequences if the number of British Islamists fighting in the Middle East grew further.
"The most important thing of all is to stop this radicalisation in the first place," David Cameron said.
"That's why my counter-extremism task force is about driving out the extremist's poisonous narrative, getting it out of our schools, out of our universities, our prisons, confronting it wherever it occurs.
"We know that the end point of this extremist narrative can mean people dead on our streets."