Plant id please - is it poisonous?

[Squash64]

I think it might be Comfrey, but I'm not sure.  It is growing in an area where children
play and the other day a 3 year old autistic boy started to eat the leaves before anyone
could stop him. The boy did not seem to suffer any ill effects, but just to be on the safe
side his parents would like the plant identified.
Thank you.

[Squash64]

[alkanet]

if not comfrey, then alkanet

[louise stella]

Going by the middle leaf it looks like comfrey!

[galina]

Going by the middle leaf it looks like comfrey!

The roots look like comfrey roots too. 

[Digeroo]

I had an idea that alkanet had red roots.  So another vote for comfrey,  people used to use it in tea, but now it is only recommended for external use.