David Abercrombie, 26, from Irvine, Ayrshire, hit the jackpot – to the disbelief of his workmates – on a Lucky Lines scratchcard from National Lottery GameStore.
He normally buys a scratchcard on his way to work on Fridays and was stunned last week when he won the top prize.
Mr Abercrombie said: “I scratched the card when I got to the site and was completely stunned.
“I said to my workmate, ‘I’ve won the top prize’. He didn’t believe me at first and took it off me to see for himself.
“Everyone was cheering when they realised I’d won.
“We went straight back to the shop and they checked again for me. They advised me to call the National Lottery line because it was such a big win. The worst thing was it was only 7.30am and I had to wait until 9am for the claim line to open.
“The minute the clock hit nine, I was straight on the phone. I can’t tell you how I felt waiting for that hour and a half.”
After speaking to Lottery operator Camelot, Mr Abercrombie signed the back of the £3 scratchcard and put it in his pocket.
He said: “I kept my hand in that pocket all day, just in case. Not much work got done, I can assure you.”
Mr Abercrombie said he has made plans for spending his windfall but is heeding the advice of his girlfriend to “be wise”.
He added: “We will be buying a bigger house so my two little girls will get bedrooms of their own. They’ve already started picking out the decor.
“A new car is on the list too, something like a Mercedes, not too flashy.
“I have always said things like this don’t happen to people like me but I was obviously in the right place at the right time.
“I think I will keep buying my weekly scratchcard and see if lottery luck strikes twice.”
Research shows builders are the luckiest profession in the UK when it comes to scooping National Lottery wins.
Mr Abercrombie bought his winning scratchcard from Shop Smart, in Dumbarton Road, Glasgow.
There is a one in 3.75 overall chance of winning a prize on the Lucky Lines scratchcard game.