I found this reference:
''Jessica Smith played the part of 'Baby Sun' in the Teletubbies TV programme. Her giggle was used on The Teletubbies 1997 chart-topper "Teletubbies Say Eh-Oh!" Though not credited for this 'performance,' she is the youngest person to have appeared on a no.1 single. We are currently trying to ascertain her precise age at the time of recording; it is certainly less than 1 year old and thought to be around the 7 month mark. ''
I thought she must be around 10 now, as my daughter is 9 and the teletubbies hasn't been on TV that long.....