Westminster chime mantel clock

Hello, I have just acquired what I believe to be a 1920s or 1930s Westminster chime mantle clock.

I am not sure of the make but it has Roman numerals and 'MADE IN ENGLAND' stamped on the dial. My query is as follows:

The clock chimes OK on the quater, half and three quarter. It also chimes fine each hour. However, when 12 o' clock comes around each time, it chimes once only. As I say, all other hours (1 - 11 inclusive) chime fine as do the quarters. Is there any reason for this?


Regards,


Colin