Actually,Berlin was bombed by The RAF(Bomber Command)shortly after The Luftwaffe bombed London(within days).Churchill instructed Air Vice Marshall Arthur Harris to strike Berlin in retaliation.Actually(from what I've read)Hitler never meant to undertake a bombing campaign against The City of London.He was more interested in the destruction of The RAF so that he could invade Britain(Operation Sea Lion)with control of the air.Some German bombers went off course and were caught over London by searchlights.In order to lighten their aircraft(and escape the triple AAA),they jettisoned their bombs.Thus began the whole thing which escalated from there!!!
Thanks, I didn't know that!