Employees at 1000 Lakeside were surprised by a festive singing flashmob in the lobby on Friday afternoon.
Rockchoir, who grabbed attention during lunch, is made up of men and women of all ages and abilities.
Choir leader Jan Moll said: ‘This is the most fantastic job in the world and I get to work with great people.’
Full uniform is usually all black when performing, but to avoid ruining the surprise they were dressed in ordinary clothes to hide in plain sight.
For information about joining visit rockchoir.com