Today ds had his friend over to play. Whilst playing in the garden ds bit his friend on the fingers, hard enough to leave some teeth marks. Ds was told very firmly no, biting is very naughty & I bright him inside immediately to remove him from the situation & he went upstairs with dh to 'help' (be out the way) & have 5 minutes with no toys etc. woke I apologised to my friend. Ds is 20 months old. He's never bitten a friend before & I don't want it to happen again but obviously it might so he will be much more Coaley supervised. What would you do to 'discipline' this behaviour as ds needs to learn this is not acceptable?