If you've got the option of a shower at the end, shorts every time. Oddly though, about two months ago a bicycle copper stationed at London Bridge during the morning commute announced at the red lights "any of you cyclists wearing shorts, make sure you're wearing trousers tomorrow." I ignored him and continued to wear my shorts and have never had my legs inspected by an officer so I suspect I made the right decision! 
	
		
			
		
		
	
			
			
 
				 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		