File:Piccadilly Circus 1972-08-29.jpg

English: Me: Let me tell you how I was able to determine the date of all of these London pictures. First off, it's likely they were all taken on one day. The changing of the guards starts at 11:00 AM, and you can see Big Ben's face at noon, 12:20 PM, and other times up to 1:55 PM. There's a public clock in this shot which seems to say 4:41, but other photos of the same clock show it's actually telling military time; it's just that in our photo, the first digit is obscured: thus it's actually 14:41, or 2:41 PM.

So both rolls of film with the London shots were processed in September of 1972. The first roll has pictures of your Poconos vacation, followed by pictures of your London trip. The second roll continues the London pictures, and ends with Tommy's first day of school and Bobby's first day of nursery school. So the London trip probably took place before the first Tuesday or Wednesday in September, which is usually the first day of school in Nassau County, as far as I can remember. You can see in this picture — the last picture in the London sequence — the London Pavilion theater advertising a Michael Caine movie, though it's not shown which one. Michael Caine was in three 1972 movies: Zee and Co., which premiered in January, Sleuth in December, and the likely candidate, Pulp on August 16th. Thus we know these London pictures were taken between August 16th and September 4th or 5th. Finally, in a bunch of the London pictures, you can see that the British flags are at half-mast. Wikipedia says this is usually done when a member of the Royal Family, or a foreign ruler, or a prime minister dies. And sure enough, there was such a death within this period: Prince William of Gloucester, on the morning of August 28th, in an airplane mishap. I'm guessing flags were lowered the day after Prince William of Gloucester died -- I assume that before the internet and cell phones, the British government couldn't coordinate all the flags so quickly after the death occured, though really, who knows?

So, in summary, I believe these photos were all taken between 11:00 AM and 2:41 PM on August 29th (or maybe the 28th), 1972.