Radiators on every day

I dont know how long this has been going on for but a couple of weeks ago and friend noticed that my kitchen radiator was on, turns out all the radiators in the house were on. This wouldn't usually be odd but its summer and its been really hot recently.

My boiler is set to summer mode and my Hive heating is set to off (frost protection only, 7degrees C).

Any idea why my radiators would be on all the time?