When should employers turn on the office heating?

With cooler weather over the past few days, the annual argument over the thermostat has started.

But with so many differing views on temperature, how do employers work out when to put the office heating on?

Jane White from the Institute of Occupational Safety and Health told BBC Radio 5 live's Breakfast: "It is often quite difficult to meet the needs of everyone."

"We have shown through research that the optimum working temperature is 21 degrees and either side of that productivity and accuracy start to go down."