First-aiders Grace and Robyn sprang into action and gave CPR to regular customer George who felt unwell and complained of chest pains after popping into the store for bread and milk.
Widower George, who has nine grandchildren and nine great-grandchildren, worked at the store as a delivery driver and then in home shopping admin into his mid 70s after he retired as an off-shore electronics technician.
George's daughter Caroline Mutch, herself a nurse, paid an emotional visit to the store to thank Grace and Robyn in person. She said: "My dad, our family and I can't thank these two ladies enough. They are a credit to Asda. When he collapsed they performed CPR on my dad and saved his life. Thankfully he's now recovering well in hospital.
"Doctors are unclear whether his heart totally stopped or it just went very slow. They are classing it as a heart attack as he's had issues with his heart since about March. The doctor at the hospital said their quick actions definitely saved him. If he'd been home alone he probably wouldn't have survived.
"I'd really like to thank Grace and Robyn for reacting so quickly and for what they did. As a nurse myself I've been involved in a lot of CPR many times I know that they did really well. I just wanted to pop in and thank them in person."
Carolyn also tweeted her gratitude to Grace and Robyn:
Twenty-seven-year-old Grace is an ambient section leader and has been at the store for four years. She said: "On the day in question a call was put out for a first aider and they also rang my phone as well so that's how I knew it was serious. I knew from the get-go that something was going on.
"A customer had alerted the customer service desk to say that a gentleman (George), had collapsed and was pointing to his chest.
"I grabbed a defibrillator and the customer who had alerted us called 999. George was conscious, but was struggling to breathe and finding it difficult to speak to us.
"With the help of Robyn and the customer we got George into a position where we could administer first aid to him properly. He wasn't breathing so I did three compressions to his chest and he started to gasp. His eyes were open but it was still unresponsive.
"We then cut his clothes away and Robyn and I put the defibrillator on which advised us not to shock him at that time which was a relief. We kept it on him just in case. We made him comfortable and talked to him until the paramedics arrived.
"It was scary as when you are trained to be a first aider that is the call you dread the most. Thank God that the first aid training paid off as the chest compressions were what saved his life. I'm so glad that Robyn was there to support me through it.
"It is unbelievable and surreal. There was a time when we didn't know that he was going to make it or not, so it was such a relief to find out that he's doing well. It will be so nice to see him when he comes back in the store.
Twenty-seven-year-old Robyn, who's the store's chilled section leader and has worked at the store for nine years, said the experience was one she'd never forget.
She says she's so glad that she's done her first aid training.
"I helped Grace get George on to his back but his whole face was grey and blue," she said. "When Grace did the compressions and he started to breathe it was such a relief. It was terrifying. Instinct and adrenalin kicked in.
"We then just kept talking to him to keep him going until the ambulance arrived.
"Every time we came into work we asked if there was any update and there hadn't been so it was lovely to see his daughter. It was so emotional."
Debbie White, our store's operations manager, says their colleagues are really proud of Robyn and Grace.
She said: "What they did was phenomenal; absolutely amazing. It was really brave of them as, although they are both first aiders, they have never had to deal with a situation like that before. If they hadn't done what they did he probably would have died.
"They were a bit taken aback when it was all over as it was so nerve-wracking."
The pair have now been nominated for Asda service superstar awards for their actions.