Sounds like your HRM is not working properly ( and there are many causes of this). You 'would not be able to run with the pack' if your HR was falling to a 100, particular with the high effort levels you mention. Degree of effort will be directly correlated with your cardiac output and the most important determinant of cardiac output with exercise is your heart rate….
Andy J2, the Half course is generally flat and fast. There's a hill at about the 8.5 miles mark but this isn't too demanding (according to my Garmin, a total elevation for this section of about 100 feet). Much more important is how the weather turns out on the day. Fingers crossed it will be calm with only a gentle sea breeze on Sunday.
He is an amazing runner, with a fluid relaxed style which looks fairly effortless and languid. Not sure if the data you've provided really means anything at all! Presumably the shorter the GCT (and about 0.2 seconds sounds pretty good), and the less VO, the more efficient you are as a runner. However this doesn't take into account cadence, average stride length, terrain, conditions, effort etc! The data you've provided for SW comes from the Salisbury 54321 50 K ultra which Steve used as a training run, running XC with legs which he describes as 'battered' so perhaps not surprising that his cadence, stride length and speed were all significantly lower than his fab run in Glasgow. Brilliant inspirational athlete and hope he wins the Ultravasan.
Personally never ran it but aware that this race was held in high esteem by the locals.
These were the comments made by one of the organisers:
End of the Road for the Swanage Carnival Road Race It is with great sadness that we announce the end of the Swanage Carnival Road Race in its current form. Following health and safety concerns from Dorset Highways Authority and Police regarding the route we have had to review the event. Despite a new proposed route being agreed this was subsequently rejected by residents. Part of Swanage’s charm is that we are out on a limb situated on an idyllic stretch of coastline, but unfortunately this means that closing the roads is an impossibility and therefore the route must be run with the traffic. Alternative choices for longer routes run from Swanage, that do not require roads to be crossed by the runners are limited. We must therefore end the long established tradition of the Swanage Road Race, considered to be the longest running County road race in the Country, after more than 105 years of known existence, and go back to the drawing board. Therefore there will be no race in 2013 but we hope to be back in some shape or form in 2014! Thank you to all who have supported our race in the past, we hope you will join us for the new event when it is launched.