A scientist who spent his career working in counter-terrorism has told a court how offenders threatened to burn down his home in Kent.
Former government scientist Nigel Cockburn, 53, is accused of setting a mantrap in his shed to stop burglars.
Mr Cockburn told Maidstone Crown Court people would break in regularly, but when he confronted them they threatened to get "50 mates to sort you out".
He also denies wounding, assault, and having ammunition with no certificate.
Mr Cockburn told the court he bought three cottages on Wood Street, Swanley, and converted them into one property.
But he said that after the nearby M25 was built "the noise and vibration was so bad I'd sleep in my car in the lay-by".
He said: "I haven't lived in the cottages for 10 years."
He spent three years staying at friends' houses but when a microlight crash five years ago left him unable to walk, he started living permanently in Cloonmore Avenue, Orpington.
Mr Cockburn said he had been burgled 20 times in 14 years, and four times in one fortnight.
Then last July, police were called to a garage fire at his property, the court was told.
Jurors heard police found a mantrap - a metal device with nails soldered to it - which injured an army explosives expert.
Mr Cockburn said he created the device as welding practice.
When asked if he intended to harm a burglar, he said: ""I've given up thinking about burglars."
He added: "If it was a trap and I'd set it from inside, how could I have got out?"
The court heard there was also a system powered by an adapted microwave designed to deliver electric shocks, there was live ammunition, chemicals, CCTV cameras and recording equipment.
Mr Cockburn said the door on the microwave in the shed had been removed for experimental purposes.
The former MoD employee told jurors: "I designed things to stop terrorist bombs exploding and designed things to find bombs.
"Everything I do is designed to search the Prime Minister's bedroom and offices, and protect the Queen."
Jurors heard that when arrested, Mr Cockburn told police: "I don't live anywhere at the moment. The Prime Minister stole this house off me."
The case continues.