@jamz Thanks for the insight, very helpful.
Same thing applies from the top of the first climb to the low point – 3.7 miles downhill but only averaging 16.7mph.
Yes, part of the problem is that this is all through a built-up area with plenty of side junctions and other hazards that make flat-out riding unwise. But you are spot on, it must impact my average.
As for the opening stretch, I will try and get into my stride quicker!