Colleagues of the missing BBC reporter Alan Johnston were set to gather in London in a show of support, four weeks after he disappeared in the Gaza Strip.

It is feared he has been abducted, but there has been no word on who might be holding him or where.

On Sunday, one of the most senior clerics in the Anglican church, Archbishop of York John Sentamu, demanded his immediate release. In a plea to the kidnappers Dr Sentamu said Alan Johnston was not their enemy.

He said Johnston had to be released as a way of ensuring press freedom in the future. “He is a symbol of ensuring the freedom of the press is not violated, an issue Palestinian journalists indeed are familiar with after facing routine attacks, harassment and arrests. And for Alan Johnston, my prayer is that he will be released. After all, he was trying to get the story out.”

Alan Johnston was last seen in Gaza on 12 March and is believed kidnapped, but no group has claimed to be holding him.