The couple have named him Lucas Philip Tindall, with his middle name honouring both Zara’s grandfather, the Duke of Edinburgh, and Mike’s father.
Lucas, who weighed 8lb 4oz when he arrived on Sunday, is younger brother to seven-year-old Mia and two-year-old Lena.
Former England rugby player Tindall, 42, today said the baby arrived so fast they didn’t have time to make it to hospital.
He said: “Fortunately Zara’s friend Dolly [Maude]… was there and recognised that we wouldn’t have got to the hospital in time, so it was run into the gym, get a mat, get into the bathroom, towels down, brace brace brace!
“The midwife that was going to meet us at the hospital wasn’t that far away so she drove up, got there just as we’d assumed the position, and then the second midwife arrived just after the head had arrived.”
Speaking on his podcast The Good, The Bad and the Rugby, Tindall revealed he cut the umbilical cord and cradled his son before taking him downstairs to watch sport on television.
He added: “The best thing about being at home was, the best thing, as soon as he’s wrapped up, you’re skin on skin, straight downstairs, TV room, golf on, and I was like, this is what me and you are doing.”
Asked how 39-year-old Zara was, he replied: “As every man will say, she was a warrior, as always. They always are.”
Lucas, who was born at the family home on Princess Anne’s Gatcombe Park estate in Gloucestershire, is the Queen and the Duke of Edinburgh’s 10th great-grandchild, and 22nd in line to the throne.
Buckingham Palace said the Queen and the duke, who is recovering from heart surgery, were “delighted” at the news and “look forward to meeting their 10th great-grandchild when circumstances allow”.
Last month Zara’s cousin, Princess Eugenie, gave birth to her first child, a boy called August. One of his middle names was also Philip.