Wikipedia says that two SAS entered by "accident".
At least six SAS entered early in the morning and searched most of the camp before finding an SAS soldier called Jenkinson. They didn't just bump into him. They had to interrogate him to check. At that point Jenkinson is the only inmate in Belsen with an armed guard and I would say free. They will have been in the camp four or more hours by the time 63rd arrived. Indeed 63rd had been waiting for clearance to enter the ceasefire zone, I don't know yet how much of that was SAS but Taylor was as good as waiting for SAS Major John Tonkin's permission to enter. Just based on Taylor's report and Randall's account, nothing much has happened other than "demanding" the best bunks and asking the SS to play nice. Tonkin in a violent incident arrests Kramer and threatens execution of guards in retaliation to any more brutality.
SAS were the first troops in to Belsen and it was no accident. I suspect 1SAS swept the entire ceasefire zone that morning and that others had also entered the camp. They rescued the first person after "quite some effort". And they forcibly removed the SS with 2,000 Hungarian guards still in the camp and about 30 Oxfordshire Yeomanry for help. I think that deserves slightly more on Wikipedia. I will provide them what citations I have. It's quite an important event. SAS involvement which is significant should be remembered.
There is another part of this story. Richard Taylor's mother's French maid from before the war who had gone back to Paris and worked in the Resistance. She was in the camp and before the arrest of Kramer they met in what has become for me a deeply significant moment. "Mr Dick, Mr Dick, it's me Anna Marie, do you. remember me ?" It must have shaken him to his core. I am trying to find more about her, at least if she survived.