Oh yes - it's steep. In fact, as the gradient is calculated on the centre line, the actual bends are a bit steeper still as this photo (credit to photographer) illustrates
The precipitous road that scales the side of Porlock Hill in Somerset, has gone down in British transport history in a similar way to that of Shap. There however the comparison ends, for whilst the Shap route climbed for many miles onto the wild and unpredictable Cumbrian Fells, Porlock Hill...
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As for Sennen, I remember getting one of the A-VAF Olympians and never thought it would make it! Mind you, it was 25 years old. The vehicle policy makes a lot of sense - elderly O/T Tridents on less demanding and more experimental services, the newer e400s on the Atlantic as that's fairly demanding (and they have an existing knowledge of likely patronage) and then some hard core stuff for the punishing Exmoor Coaster route. I wonder if the EC is even beating FSW's expectations for a commercial punt?
Out of interest, when does the season finish on the Exmoor Coaster?