Then you would be highly unprofessional. I'm on a three-month term where I am, it's fairly standard around here. I would expect to work as normal during those months, and other people that I have watched go through notice have done the same.

I'd be in breach of my contract, and (in theory) my employer could sue me. 3 month notice periods are very common for senior people in the UK so employers work with it. It also benefits the employer because it means they're less likely to have an unfilled role - if I resign they have 3 months to replace me. Less notice means they have a serious problem after I leave but before the next person starts.

3 months isn't even the longest I've known. I worked with some people a few years ago who were C-level execs in a manufacturing business who had to give 6 months notice.

That would be unprofessional.

On the other hand you can often negotiate a shorter exit period; it will depend in some sectors _when_ you are leaving as much as how much notice.

e.g. as I understand it, in government sectors in the UK, you might find your notice period runs out at the beginning of any new Budget regardless, or you might find yourself on gardening leave.

And if you travel into London you might find your final date has as much if anything to do with your travel season ticket loan period!

Cuts both ways, too: longer notice periods for employees resigning are matched by longer notice of redundancy (and statutory pay), as well as other redundancy protections, like they can't make you redundant just to hire someone else they prefer. It's a very different world to the "at will" states of the USA.