Qatar Airways bomb threat incident

Luckily it seemed to be only a hoax but it frightened passengers and defense forces in UK .
What happened on flight Doha -Manchester on 4 th of August ?
A UK passenger sent a written notice to the captain about a bomb he had hidden on the plane .The pilot informed the defence forces which sent a military fighter jet to "escort" the plane .
What was the aim of the passenger with this threat ? How can a military jet change the course of the events ?
Yet there is no answer on those questions .
One thing is sure -there was no bomb on the plane .

source