Thomas and Elisa Milam called the police after they heard noises in their house at night, not realising it was the robotic vacuum cleaner they had bought for Christmas.

The North Carolina couple barricaded themselves in their bedroom with a gun until police gave the all-clear.

Writing on Facebook, Mr Milam said: “All my military training came back to me. I started analysing the path the intruder would take, their line of fire and where we should be to decrease our risk of getting hurt.

“All I kept thinking about and listening for was my little two-year-old next door to us, alone.”

The police officer who solved the mystery reportedly located Mr Milam and asked: “Sir, I have one question. Is this Roomba yours?”