Treason - Noun - the crime of betraying one's country, especially by attempting to kill or overthrow the sovereign or government. I'd say that's covers it eddie.
//I could imagine Cameron doing the same thing if the opportunity arose. //
Yes indeed - but I don't think he was possessed of the brains or the wherewithal to attempt it. To be perfectly honest - and I've said this before - I think there are a lot of people who have/would have done likewise. I think Mrs May was trying her best to keep us in while all the time telling us she was negotiating Brexit .... and I vote Conservative so I can hardly be accused of political bias.
I agree Naomi, Mrs May tried her best, but was left with an impossible task, not helped by a lot of her own party knifing her in the back at every opportunity, including many of the current cabinet.