A total of 256 people were on board last December when parts of the engine on the Boeing 777 broke off.
“Considerable amounts” of debris fell on Broxbourne, on 27 December 2012, the Air Accidents Investigation Branch (AAIB) report said.
The Royal Brunei Airlines jet returned to Heathrow, where he landed safely.
AAIB officials described the incident as “serious”, with the jet becoming the 15th to develop the same engine problem.
Their report stated that having also taken off from Heathrow, the Dubai-bound jet was flying at about 15,000ft (4,572m) when crew heard a “loud rumbling” noise, prompting the 56-year-old captain to turn back.
It was later found that the right-hand Rolls-Royce Trent engine’s inboard thrust reverser was missing a large amount of material from its inner wall and, consequently, the exhaust nozzle had been damaged and become loosely attached.
The AAIB said a number of inspections and modifications were already in place “to try to mitigate inner wall damage and potential parts liberation.”
Its report added that Boeing had advised that the USA’s Federal Aviation Administration may mandate inner-wall replacement on all Rolls-Royce-powered Boeing 777s.
No passengers were hurt in the incident. The AAIB report gave no details of any damage to the property In Broxbourne or if anyone was hurt on the ground