Here, two things must be done. The first thing is to adjust the watch to the world's most standard time. Under the GMT clock there is the exact length of the British Foot, which is determined by the foot length of John who usurped Richard the Lion Heart and signed the Magna Carta. It is said that in the early thirteenth century, there was no uniform standard in Britain, which caused a lot of trouble for trade. So many ministerial meetings were held to discuss the matter, but there were different opinions and no unified standard was established. So John stepped on the ground angrily and pointed at the sunken footprints to solemnly announce to the ministers - "There is a foot, let it be the measure from this day forward." That is why foot is Foot in English. The second thing is to take a picture of yourself crossing two hemispheres on the first meridian. We decided that Dad would stand in line here. I took my daughter to visit the Observatory first. When we finished all the visits, Dad was still queuing in the cold wind. At first, I was worried about whether it would be 17 o'clock closing time, and staff would ask all tourists to leave, because foreigners still value the time to go to and from work. Unexpectedly, until we finished shooting at about 17:45, no one came to the end of the scene, and at this time there were many people behind us. So, I think that visitors are not allowed to re-enter at 16:30, but if they have already entered, they will still wait until all the people in the queue have taken photos before closing the door. It's very intimate. After an hour of queuing, it's finally our turn. It's just to see it - Benchu meridian, the dividing line of the eastern and Western hemispheres. The East and west sides of Benchu meridian are designated as the eastern meridian and the Western Meridian respectively, and the international zero. Point, where a time begins. Finally, I got a picture of two hemispheres with one foot - "Good morning to today with the right foot, goodbye to yesterday with the left foot. Nearby are the Maritime Museum and the Katie Sark. Tickets are not cheap, but London Pass is available. The "Katiesak" is the fastest sailing ship in the history of sailing in the world. It is called "Downwind Whisky" and represents the peak of sailing technology. It was built in Scotland in 1869 and has a history of 146 years.