It first dawned on Tracy Mitchell that this was no ordinary fare when she pulled up to the doors of the Lindo Wing, and was met by a sea of cameras and photographers.
A press officer asked her if she knew who she had been called to pick up and explained that it was Kate's mum and dad. "I just looked at him in disbelief and said - really? Are you joking?"
When the Middleton's got into the cab Tracy says they were talking quietly amongst themselves with Mrs Middleton spending some of the time on the phone. It wasn't until they got to Kensington Palace that Tracy spoke to them.
"I switched the intercom on and congratulated them and they said thank you very much and they were really quite nice."
"After I congratulated her she waved her hands nervously as if to say it was all a bit weird".
"I just laughed and said imagine what it was like for me - the cab driver!"