No one in my office takes a lunch break. Is my employer obliged to give me a break from my desk or do I need an informal approach to get my just deserts?

The answer, really depends on the length of your working day, the type of work you undertake and also what your contract says. There is no legal right as such to a lunch break, but generally all adult employees working more than 6 hours a day have the right to a 20 minute unpaid rest break away from their desk. Your employer is not required to make you take the rest break, or to check that you have taken it, as long as you have the ability to take your rest break if you wish.