The supersonic robbery

It was the Queen’s Jubilee and everyone was out on the streets, playing games like tag, running around in the streets and eating food. Jack was among them, though he wished to be inside in such a hot day. The RAF planes were flying about, dancing in the sky.

A tremendous boom filled the street as the planes hit supersonic speed.

As he recovered from the blast, he decided he was getting tired and started to head for home.

While he was making his way, he saw a man walking in his direction, muttering to himself and shaking his head.

Jack opened his mouth. “Um, sir, do you need any help?”
The man looked over and said: “Nope, unless you happen to know the way to Jack’s Detective Agency.”

Soon, Jack had a new customer.

The man, Mr. Johnson, owned a cake shop. He expected to make more money over the Jubilee, but instead had gotten a cake stolen.

“So did you see the robber’s face?” asked Jack.

“No, but they were wearing a shirt emblazoned with ‘s’.”

“The Shadowblades?”

The Shadowblades were a gang.

As Jack walked to the Shadowblades’ headquarters, he saw their leader, Max.

“Hello, Jack.”

Jack asked Max: ” Where were you an hour ago?”

“Oh, I was at the local store. I heard the sonic boom and I went outside to watch the RAF fly. They’re graceful. Why’d you ask, anyway?”

“A cake was stolen,” said Jack “You owe Mr. Johnson £50.”

How did Jack know?