Both mum and baby are doing well after PC Robert Morgan helped with the delivery after being flagged down in the middle of his shift.
The new baby girl doesn't have a name yet but she's happy and healthy.
More top news
Shoppers evacuated from Topshop in central London after a 'fire breaks out' in the basement
Police are appealing to find an absconder from a mental health unit in Haringey
Transport officials meet with Google in a bid to bring driverless cars to the streets London