This is bunkum
Here's a little experiment you can carry out right now as you read this post
Your computer is about a foot away from you and you are are focussed directly on the screen reading these words
Now
Notice how much else is in your periferal line of vision
Notice how it would be impossible for anyone to pass close to your 'direct point of vision' ( your computer ) without you being aware
Well that is what Heri just told me.
Anyway if we are going to get down to the nitty gritty, Jane was never closer than 67.5 degrees to Gerrys line of vision cos he was looking in an ESE direction when he was looking at the baby Kate was in a Southerly direction as she left the Tapas reception and that gradually changed to an easterly direction.(behind him)
Work that out, Icabod !
.... and the same when she had passed Gerry, except that he was looking in an ENE direction when speaking to Jez and Jane gradually moved from behind him into a Northerly direction.
So once again Jane was always at least 67.5* to Gerrys line of vision when talking to Jez. Way beyond his periferal vision!
BOTH SIDES ARE WELL BEYOND HIS PERIFERAL VISION .... Sorry Icabod
And

to Jane and Gerry