Yes, the CAA considers the River Thames in London to be a 'congested area'
Talkdown, do you have a reference for that? The Order states the "congested area of a
town, city or settlement - I suppose you could argue that house boats are "settlements". It also stated " ‘Congested area’ in relation to a city, town or settlement, means any area which is substantially used for residential, industrial, commercial or recreational purposes;"
I'm discussing this purely from a legal standpoint but if one ditched in the Thames with no loss of life have you contravened the ANO?