Worcester Digistat DT10RF Programmer, wireless thermostat for boiler. Compatible with various Worcester Greenstar boilers, as in photo. Allows you to program different temperatures for different times of day (but not different days of week), override programmed temperature, and put heating in holiday mode for required number of hours or days. Can be wall-mounted. Complete with instruction manual.
20 years old and still working perfectly but we've now gone smart.