Verbal's left me in lurch

Dear James, I HAVE accepted a new job and been given a start date. I am on three months' notice and gave my boss verbal notice on accepting.

- James Innes, best-selling careers author and founder of The CV Centre, solves your work problems... James says:

However, I handed in my written notice a couple of days ago and have now been told my last day at my current workplace will be a week after I am meant to start my new job.

I gave my boss enough notice but he is not budging. What can I do about this?

Greg, Southampton?