Gerry, 41, and Kate McCann, 42, lined up at the first ever Miles for Missing People in London's Hyde Park, alongside other families whose loved ones vanished.

The couple wore matching white T-shirts bearing a smiling picture of their daughter and the words "Don't give up on me".

Mrs McCann and her husband Gerry, from Rothley, Leicestershire, were on holiday with their three children in Praia da Luz, Portugal, when Madeleine went missing in May 2007.

In an earlier statement, Mrs McCann said: "Gerry and I know the pain that having Madeleine missing has caused us, but sadly we are not alone.

"There are thousands of families across the UK waiting for news.

"That's why Missing People provides support for missing children, vulnerable adults and families left behind, and we want to do all we can to help them."

Rachel Elias, 40, from South Wales, sister of former Manic Street Preachers guitarist Richey Edwards, who went missing in February 1995, was among the runners.

She said: "I am running it for my brother and for all the other people who have disappeared and to support the work of this charity.

"They have been a tremendous source of strength over the last 15 years.

"(Edwards) was legally declared dead in November 2008, but there is no certainty over the loss, there is that hope.

"There are moments when you swing between hope and despair, sometimes you feel different emotions at the same time which can be very confusing."

Nicki Durbin, 41, from Suffolk, whose son Luke disappeared in 2006 aged 19 following an evening at a nightclub in Ipswich, also supported the event.