Mum Jo Paine had called 999 when her baby son Harrison stopped breathing just days after she'd brought him home from hospital after his birth.
PC Steve Norton responded to the call and took immediate action, scooping the newborn up in his arms and sprinting to the nearby St George's Hospital in Tooting.
Despite the fact he was wearing full police body armour, he managed to get there in enough time to allow doctors to stabilise Harrison and save his life.
Describing the drama, just before Christmas, Jo said: "My world crashed before my eyes. He hadn't woken up for his feed, his skin had turned grey and his eyes were still.
"I immediately lay him on my bed and starting chest compressions and rescue breathing into his mouth and nose, just as I had been taught at hospital days before Harrison and I had been discharged.
"He responded and made a noise before he started to shallow breathe. PC Steve Norton arrived at my door and immediately handed Harrison over to him.
"I did this with complete trust and confidence. At that moment in time, I believed that he would do all he could to help my baby."
After being reunited on ITV's Good Morning Britain, PC Norton said: "Jo just handed him to me and said 'I don't know what else to do' and I grabbed him and ran.
"I will never forget the moment Jo handed Harrison to me; I looked down at his face and it dawned on me that this could have easily been my baby who was a toddler at the time.
"I knew that every second was crucial to for this tiny baby who was not breathing properly. Jo was the one to initiate CPR and I have no doubt that her actions allowed me the time to get him to hospital.
The officer went on: "Seeing Harrison and Jo happy and well in the run up to Christmas has been the most worthwhile and heart-warming experiences of my career."
my son I'd want to get him help as quickly as possible."
Jo said Steve had now become a friend as she handed him a keyring from her and Harrison engraved with the words 'forever thankful'.
She added: "There's no words that can describe my gratitude for what he did. It was incredible.
"And I would say to new mums, take a CPR course, it really is worth it."
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