Trying to remember, I think it was always the case that London had more trans Atlantic routes than Paris, & more frequency, too. There may have been certain places in the USA/Caribbean area which only had services to Paris but, generally , London had the greater number of routes & frequencies in my recollection. It is interesting to note that London - SFO was only about 4 times a week in the early to middle ‘60s, LAX was once daily, MIA didn’t have a service at all until the latter part of the decade, & even JFK- London was only served about 3 times daily by BOAC (not counting US airlines here, but their services - TWA & PAA - were about as frequent & extensive as BOAC). To my recollection, there were no services - by any airline - to places such as Seattle, San Diego, Portland, Las Vegas, Denver, Dallas, Houston, Orlando, Charlotte, Atlanta, Minneapolis, Detroit etc. How times have changed !