Found this on the RHS site.
Flowering: Some cultivars can be more prone than others. Remove flower stalks as soon as they appear to prevent them weakening the crowns. Flowering is usually worse after wet summers or where high nitrogen feed has been overused.
The reason for asking is that we have 4 plants and they all tried to flower this year
My logic was - either all rhubarbs flower or we just happen to have 4 females