Madeleine McCann went missing at the age of three in May 2007, during a family holiday in Portugal

HEARTBROKEN Kate McCann has been overwhelmed with emotion writing a book about her daughter Madeleine's disappearance, friends revealed last night.

Kate is now close to finishing the deeply-personal account of her nightmare, which she hopes will raise millions of pounds for the dwindling fund set up to find her daughter.

Any money will pay for private detectives to continue the search for Madeleine, who went missing at the age of three in  May 2007, during a family holiday in Portugal.

Last night a close friend said: 'At times it has been heartbreaking for Kate.

'Not surprisingly, there have been many tears. But Kate has been strong and carried on for Madeleine's sake.'

Kate, 42, a doctor from Rothley, Leicestershire, has been using extracts from her personal diary written in the days after Madeleine vanished.

She has also been relying on family and close friends to help jog her memory.

The friend told how Kate had been overwhelmed with emotion at times as she re-read the chapters.

But she insisted she had to carry on to help her desperate fight.

The friend said: 'She is adamant it will be her very own account ' written in her words ' and has turned down offers by her publishers of a ghost writer.'

Kate has been helped by her husband Gerry and close friend Fiona Payne, who was also on the ill-fated holiday in the Algarve resort of Praia da Luz.

The book was originally due to be published on April 28 ' just before the fourth anniversary of Madeleine's disappearance.

But publishers Transworld postponed the release date by a fortnight because it would clash with the 'media frenzy' surrounding the wedding of Prince William and Kate Middleton on April 29.

Heart consultant Gerry, 42, has also postponed his own money-raising event ' cycling from Portugal to England ' because of the royal wedding.

Kate's book, simply entitled 'Madeleine', will now be published on May 12. That is the day of Madeleine's eighth birthday, underlining the book's central message that her parents are convinced she is still alive.

The couple, who have five-year-old twins Sean and Amelie, have publicly told of their fear that lack of cash could make it impossible for them to continue searching for their daughter.

Gerry's marathon fund-raising cycle ride from Portugal to England has been put back until the summer.

Gerry and three friends were due to begin the gruelling 2,000-mile journey from Praia da Luz to Rothley on May 3.

A family source said last night: 'Gerry is disappointed because he was looking forward to the challenge to continue raising awareness and funds.'