THE sister of captured aid worker Alan Henning sent a poignant message to her brother on his birthday in August.

Gill Kenyon, from Bury, posted a black and white picture of the pair together as youngsters on Twitter on his 47th birthday.

Referring to her brother by his nickname – Gadget – she wrote: “Happy 47th birthday to my little bro Gadget/Alan Henning. Can’t wait to have a party on your return, love you bro xx.”

Islamic State (IS) jihadists are threatening to kill the 47-year-old married father-of-two who is thought to have been kidnapped around Christmas time just after crossing into Syria from Turkey.

Foreign Secretary Philip Hammond said Mr Henning's family was “going through hell”.

British forces do not know where Mr Henning is being held hostage, he added.

Threats to kill the former taxi driver — who travelled from Bolton to Syria in December last year — were made at the end of a video showing the brutal murder of British aid worker David Haines.

Mr Hammond said: “If we knew where he was, we would be able to look at all sorts of options but we don't know where he is.

“We have considered every possible option to support these kidnap victims.”

Mr Hammond said Mr Henning's family was “going through hell” but that they understood there was a limit to what the Government could do to help him. He added: “It is a terrible time for them. We are doing everything that we can to protect him.

“They understand, because we have explained to them in detail, the limitations of our abilities. We are dealing with a very barbaric organisation whose values are completely different from ours.”

Close friend of the captured aid worker – Kasim Jameel – says he is in daily contact with the hostage’s family.

Bolton aid worker and fellow volunteer Mr Jameel, who travelled to Syria with Mr Henning, said: “I had hoped he would be home by now because he is just a humanitarian who travelled with us to make a difference.

“That is all he wants to do. He told me he gave up Christmas with his family to help. If he could make a difference to one child and bring a smile to their face he was happy.”

It is believed Mr Henning was captured just 30 minutes after arriving in Syria. It was his fourth humanitarian trip to the country.

Mr Henning, from Eccles, travelled from Bolton to Syria in December last year with eight other volunteers from the town.

Mr Jameel added: “He is a genuine person a totally amazing guy. He just could not sit and watch what was going on. He wanted to go to make sure the supplies were reaching the people. That’s why he went.”

Mr Jameel who calls Mr Henning “Gadget” because of his love of technology, said his friend was in his thoughts and prayers and that he was doing what he could to support his family.