The Scots rally driver Colin McRae, who was killed along with his five-year-son in a helicopter crash, found it hard to come to terms with the end of his career and "struggled a bit with the whole retirement thing", his widow has revealed.

Alison McRae, interviewed for a new book on her husband, said he wondered what he could do with his life once he left the world of the professional sportsman behind.

The book also carries a moving tribute by McRae's daughter, Hollie, who is now 14. She spoke of "the big, friendly family man" and said: "A bit of me dies slowly inside every time I think I won't see Dad or Johnny again for the rest of my time on Earth."

The former world rally champion was at the controls of a helicopter that crashed and killed himself, his son Johnny, six-year-old family friend Ben Porcelli, and another friend, Graeme Arthur Duncan, 36.

The helicopter crashed in Mouse Valley near Larkhall, South Lanarkshire, on September 15, 2007.

A sheriff later ruled McRae unnecessarily took the helicopter on a risky low-level flight into a heavily wooded valley to thrill his passengers.

In the book, Mrs McRae, who described Colin as her "one and only love", recalls her husband's outlook after retiring from rally driving a year before the accident.

She said: "There was a big thing in Colin's head that kept saying, 'What am I going to do with my life now?'

"There was this part of him that just felt useless. He'd say, 'Alison, I can't do anything apart from driving cars.'

"I'd tell him, 'Colin, you're the best in the world. You try to explain that to a person who works in a hospital – they would all strive to have your talent, your career'.

"He would reply, 'You don't understand. To me, driving is so easy, it's not like I've achieved something'."

Daughter Hollie, who was nine at the time of the accident, writes in her foreword to the book: "Johnny and I used to love it when Dad came home from rallies because he would always bring back a present for us.

"Now that I'm older, I've realised that I was wrong waiting for the presents to come home. I should have been waiting for Dad. The saying is true – You don't know what you've got until it's gone."

The teenager said her father had also taught her to stand up for herself and for what she believed in.

The book also features tributes to McRae from Scots race legends Sir Jackie Stewart, David Coulthard and Dario Franchitti. Stewart said: "Colin was much admired because his driving was so spectacular."

Franchitti said he had received a text from McRae on the day of his funeral: "After the accident in 2007 I was coming back to Scotland for the funeral.

"I'd had my final race of the season in America the weekend before.

"When I got off the plane at Glasgow Airport I turned on my UK mobile and there were three messages. The third was from Colin wishing me luck in my last race.

"That stopped me in my tracks. I just couldn't believe he was gone."

In a ruling in September 2011, Sheriff Nikola Stewart said McRae had been guilty of imprudently and unnecessarily taking the helicopter on a risky low-level flight into a heavily wooded valley to thrill his passengers.

He had not held a current flying licence or a valid rating for the Eurocopter Squirrel.

But McRae's father, Jimmy, said his son was a good pilot who was well-equipped to fly the helicopter.

He said: "We still believe we will never know what caused the crash, but we were never in any doubt as to Colin's prowess as a fine pilot."