I work in marketing and have an offer at a new company where I will not be performing substantially the same work. This is in my offer letter for the new place:
“By accepting this offer, you confirm that you are able to accept this job and carry out the work involved without breaching any legal restrictions on your activities, such as restrictions imposed by a current or former employer. You also confirm that you will inform [redacted] about any such restrictions and provide [redacted] with as much information about them as possible, including copies of any agreements between you and your current or former employer describing such restrictions on your activities.”