 In " rhubarb " operations over France , Johnson 's wing commander , Patrick Jameson , insisted that the line @-@ astern formation be used which caused Johnson to question why tactics such as the finger @-@ four had not been universally adopted . Johnson criticised the lack of tactical consistency and when his squadron flew top cover , he often changed to the finger @-@ four as soon as they reached the French coast , hoping his wing leader wouldn 't notice . 
