A former British soldier fighting Isis militants in Syria was enraged after being questioned by UK border forces for six hours upon his after return to Britain for Christmas.
Jamie Read, 24, said he was left "raging" by the interrogation at Heathrow Airport.
Officials wanted to know if he and comrade James Hughes, 26, were paid for their exploits in the war-torn country.
Read told The Sun of his questioning by UK officials: "I was raging. They kept asking why we went, who we were with and were we being paid? We weren't, of course."
The British government is not committing ground troops to the conflict in Syria. Usually authorities are on the look out for people who have who left Britain to fight for Isis, rather than against them.
Read insisted he still hopes to travel back to Syria after Christmas, citing "unfinished business".
"My family were nervous and obviously worried about my well being – we have gone into an unknown world.
"But I'm a firm believer that if you want to do something you have to do it, not talk about it."
Read said 11 of his comrades have died in fighting against Isis.