Just to set the record right the following is what transpired.
On 24 June 1982, a BA flight enroute to Australia flew into a cloud of volcanic ash thrown up by the eruption of Mt Galunnang, Indonesia resulting in the failure of all four engines, although the reason for the failure was not then apparent to the crew or ground control. The aircraft was diverted to Jakarta in the hope that enough engines could be restarted to allow it to land there. The aircraft was able to glide far enough to exit the ash cloud, and all engines were restarted (although one failed again soon after), allowing the aircraft to land safely.
Three weeks later on July 13th an SIA B-747 (9V-SQD) enroute from Singapore to Melbourne flying the same route suffered the same fate and much the same outcome. Both flights were at night time.
In spite of the time frame between the two incidents the Indonesian Aviation Authority had not issued any Notams and knowledge of the first incedent had not been diseminated.