I think that if his alibi held water, in any way, he would not have been put under the scrutiny he has been under. He would not have been splashed all over the media. He would have been cleared as a POI, in this case.
If the police thought he was 'merely' a part of a bigger plan. I think they would have been a lot quieter about their actions. Put a gag on the media, put Spedding under 24/7 surveillance, allowed him some movement, monitored him in every way that they could, followed the trail.
Instead they have done quite the opposite.
They have him bundled where his movements are strictly limited, he must report to the police regularly, they allow the media to speak of him at every opportunity ..... (except now of course, due to subjudice).
BBM. have they done the opposite? IDK