Gillian Whittaker had just dropped off her three year old at his grandparent's home and was driving back with husband, Mark, when she suddenly went in to labour.
But unlike her first time around, the 37 year old mum from Stotfold, Beds, did not have the time necessary to make it to Lister Hospital.
"When I had Simon I was in Lister Hospital for about 10 hours so I thought I had more time," she confessed, "But I started having contractions and realised the baby was coming fast so dialled 999 for an ambulance."
"Mark was driving and thought we could make it to Lister but I said: 'We need to pull over' as I felt like I needed to push. The emergency responder... told me to lay down in the back of the car after we stopped on the hard shoulder. I didn't want it to happen but all I could think was that I needed to push."
Seeing a car parked by Junction 4 for Hatfield, police officers, Neil Crosier and Ben Harper stopped to investigate.
Upon realising that the baby's arrival was imminent, they closed off the inside lane and hunkered down to help.
"The police officers had just started their shift and were driving along the motorway when they saw my legs sticking out of the car," Gillian laughed. "Neil held my hand and tried to calm me down - I think I squeezed quite hard!
And it is in gratitude for this aid that the couple have chosen to give their son TWO middle names after the police officers who helped bring their little guy in to the world.
Even when the ambulance arrived the drama wasn't over: "We were driving towards the hospital (and) I had a couple of contractions and the paramedics Lorna and Ruth said the baby was crowning so we stopped again."
Weighing a healthy 6lbs 12oz. Sebastian Neil Ben Whittaker made his appearance five minutes later and three whole days before his due date.
"We are just so grateful for everyone's help," said Gillian. "(To) the policemen who stopped and closed a lane of the A1(M) - that was really nice although I wasn't worried about protecting my dignity by that point! - and the two paramedics Lorna and Ruth who helped deliver my baby."
"Both me and Mark are so grateful they knew what they were doing."
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And what does big brother think about the adventure? "I think… Simon thought it was quite exciting as he's got an emergency book which has an ambulance attending an incident on a motorway.
"He keeps saying that's how I had little Sebastian!"