Dear Stephen,
Yes, Daddy was trying to keep you out of the kitchen. We don't really want you vanishing down the pipe cavities while the plumber works.
He unlocked the door and opened it. He looked round, no cat. He slid in, carefully not opening it wide enough for you to get through, and closed the door behind him. He made his cup of tea, keeping an eye on the kitchen door in case it should mysteriously open. It did not. He opened the door a crack and looked for cats. No sign. He rushed out, trying not to spill his tea, and closed and locked the door behind him again (by which point, yes Mummy was laughing).
So why, five minutes later, did we hear scratching coming from inside the kitchen door, and have to let you out?
Regards,
The baffled staff
P.S. By the way, Daddy now acknowledges that your ninjitsu is superior to his own.