British journalist John Cantlie held by IS 'still alive'
The photojournalist, who has been captive for more than 6 years, is the last remaining UK hostage held by IS.
Wallace described Cantlie as the most public and prominent British hostage. The UK official said he believes him to be alive in response to a question, but did not say where he was believed to be held.
In recent years, there have been mixed reports concerning the whereabouts of Cantlie.
In July 2017 there were unconfirmed reports in Iraqi media that he had been killed in Mosul. In October 2017 an IS fighter told French Magazine Paris Match that he had seen Cantlie in recent months in Raqqa.
Cantlie has appeared in the role of a Western journalist in a number of IS propaganda videos. His most recent appearance was in 2016.
The video was part of a series entitled "Lend me your Ears”. The journalist introduces himself in each clip as a "British citizen abandoned by my government". This refers to the UK's refusal to negotiate with IS for Cantlie's life, and its long-standing policy of not paying ransoms to armed groups.
Cantlie is an experienced war photographer who has covered Iraq, Afghanistan, Somalia, Libya and Syria. He was first kidnapped in Syria alongside Dutch photojournalist Jeroen Oerleman. They were rescued by members of rebel Free Syrian Army after one week.
He was then abducted alongside American journalist James Foley, who was beheaded by IS in 2014.