More than likely the evohome was requesting a very cool flow temperature for just one room and the 'on' time was extremely short. The only way to confirm would be to lower that room temperature if possible.
Thanks for that!
I suppose that makes sense as the pump would activate before the boiler fired & if at any point during the ''activation sequence'' the room temp momentarily rose it would cancel it & start the ''deactivation sequence''. Then if at any point during that the temp dropped slightly it would restart the ''activation sequence'' when it next had time to do that...
Evohome apparently has a built in boiler cycling condition to prevent it turning the boiler on & off too often...I believe it is every 10mins which could cause this.