Much like a normal Advent calendar, the Baxi calendar will provide a tasty chocolate treat for each day of the Christmas countdown, but with extra-special surprises behind some of the doors.

Two hundred out of the 2,000 calendars have a secret ‘brass’ door, which will reveal a range of exciting prizes just in time for Christmas, from a SONOS speaker or a 55-inch TV, to an Apple Watch series 6 or a Nintendo Switch.

Lucky installers will also find a host of other goodies behind the brass doors, including Apple AirPods Pro, SONOS beam soundbar, Christmas gift hamper, Lay-Z-Spa, Amazon Fire tablet, Ring Pro video doorbell and even an iRobot vacuum cleaner.

The Advent calendars are available on a first-come, first-served basis only.

Andy Workman, sales director at Baxi, said: “Although 2020 has been a challenging year, installers have gone above and beyond to look after customers and provide crucial heating and hot water services.

“We wanted to give heating engineers a boost of positivity as the year comes to an end to thank them for all of their hard work.'