Motorcycle Safety & Driveability: Dad, Mum and toddler, passenger footrests, safety helmet

Question
In the UK, is it illegal to ride a motorcycle with a pillion passenger and a small child in a sling worn by the pillion passenger?

Answer
They must be big enough to reach the footpegs.

Pillion Law

Without going through all the road traffic acts, here's a brief synopsis:

1) You must hold a full licence for the machine you're riding, wear a safety helmet etc.
2) Your bike must be adapted to carry a pillion (a rear seat and passenger footrests).
3) Your pillion must wear a safety helmet and sit astride the machine facing forward. There's no legal age required for riding pillion but he/she must big enough to hold on, sat astride with feet on the foot pegs (so there is a size limit) and able to fully understand the instructions you give.

Now the next question is how many people many be carried on a motorcycle - TWO, so will the toddler be classed as the third person,

Hope this helps
Nigel