Exceptional circumstances would normally be limited to things outside your control and of a fairly major impact.Real life examples I have encountered:Colleagues wife was killed on a car crash. He was granted immediate compassionate leave and on deciding not to return to work, but to stay home with his two kids, he was not required to return to work for his notice period.Colleague was informed that his ageing father had months to live due to pancreatic cancer. He resigned to spend quality time back home and was allowed to go straight away.Kind of puts it in perspective, eh?As EC says, you're likely to get away with it, but don't pretend that HR or the project are being unreasonable. You are in breach if contract and your word is is no longer your bond. Whenever someone simply walks out, it is their own colleagues that have to pick up the extra workload.I also presume your wife's new job is sufficiently senior that you won't need to work again? Or at least not in a job that requires your current employer to provide a positive reference?The classy answer would be to work your notice.