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.
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London and the worlds has united on Twitter in defiance of the West minster attack #prayforlondon #wearenotafraid
London was today a city of sirens and half mast flags in the wake of another terror attack.
MPs said they would "carry on" and go to work "as usual" in defiance of the terrorist attack outside the Palace of Westminster.