Even though it seems to me there isn't any evidence to suggest Nevill called either Jeremy or the Police, lets assume JB didn't call the Police until 3.36 as Mike is suggesting.
By Jeremy's own statement the call HE made to the Police lasted 10-11 minutes including the time he was kept on hold. At no time during this call was it ever claimed that he was told that the Police had already received a call and had already sent a car.
He then was supposed to have called Julie AFTER the call to Police, putting this call at 3.47 at the very earliest, which is 17 minutes AFTER the time JB claimed he called her and which is disputed by evidence of three people living in the house with Julie in London, all of which put the time at nearer 3.00am.
This would place the call to the Police at 26minutes AFTER Jeremy claimed his Father called him. That's a long time to react.
JB was asleep in bed when he got the call from his Father so wasn't dressed. The call to Police finishes at 3.47 Earliest, he then calls Julie, he dresses and is overtaken by Police at approx 3.58 driving at 30mph towards Whitehouse. Only 11 minutes after the end of the call to Police.
In my humble opinion, these timings are unrealistic and far less believable than one single call to the Police, as always claimed and never disputed before, at 2.26.