This is what happens at a citizenship ceremony (or, at least what happened at mine in December).
I got notice from the Home Office that my application was successful (yeah). The next day I got a form from the CIty Counicl telling me that I'd been booked for December 22. In Cov they only do one a month. I had to send in a form listing the names of my four invitees, if I planned to pledge or affirm allegiance to the Queen (the latter is secular) and if I minded shaking the hand of the town's Mayor.
The service was scheduled for 2-4. In reality in began at 2:30 and was over by 3. Coming to the Council, they check your id against the official letter and sit you in an assigned seat. The numbers getting citizenship were around 40. Mostly South Asian of all ages, younger Caribbean/African, and then some East Europeans. It seemed that about 50% were Muslim, judging by the names. I was the only West European/American. Dress varied. I came in a suit and tie, others came in track suit pants. The room was held in the council chambers, very official, but loads of children running around chaotically.
The worst part was for having to listen to Elgar on a CD boom box for 30 minutes waiting for the ceremony to begin.
Then the thing begins, a woman from City Council comes in, we stand for the Lord Mayor in regalia, and the woman tells what's going to happen. The first thing you see in the room is a larger than life-sixe photograph of ELizabeth on a tripod. The UK flag forlornly draped on a pole that seemed randomly placed in the room.
Whenever the woman with the mike mentioned Her Majesty, she turned to look at the photograph and slightly nodded her head. Then the Lord Mayor spoke (a low talker). This was the sort of Vegas like moment: her with the mike, him in Liberace dress.
Then all those who swear do so in a group, followed by those who pledge. Then all say the citizenship thing. Then we sat down and waited to be called by name to come up and receive a scroll with our name on it, like graduation. When you got your scroll, you shook hands with the Mayor and posed so that your friends could take a photograph. One Asian guy came alone but he had a camera and the Vinnie Jones look-alike guard took the photograph for him!
Then you walk over and get a folder with the official certificate and a packet telling you how to apply for a passport. (The packet can be gotten from any Post office incidentally, but not the certificate).
After everyone had their scroll/folder. We went to another room for tea and biscuits. That was it.
One word about the certificate. You have to send it in for the passport and they fold it! to fit in the envelope. It came back even more dissheveled from the UK Passport agency. BTW, it took a week to get the passport through the post office's service. The UK passport is couriered to you. They mailed back my US passport in a regular second class mail envelope (thanks guys, any idiot could have felt that it was a passport).
The day was very British, a bit chaotic and cheesy, but worth doing. It really doesn't take long and there is that frisson when you actually say the allegiance. My girlfriend was worried that I'd start laughing when I affirmed allegiance to the queen, but I just broadly smiled, since after all, Paris is worth a mass.