South Downs Way, Day 6 - Bramber to Ditchling - Don't mess with the yellow hats

Because the path was on a ridge the morning often began with a mile of steep uphill walking. Just outside Lewes, there were people ahead of us on the ascent.
A large mixed-sex group of people, around thirty years old, mostly wearing yellow beanies.
Some appeared to be capable walkers while others were frankly shambling. 
What did they have in common (apart from the yellow hats)?
Why were they here?
Due to their mixed abilities, they were already strung out.

'Its going to be too hard to overtake all that lot on this steep bit. And we don't want to end up in the middle of their group.  We'll just have to tuck in behind.'

But, to my horror, only minutes later, I found our normal pace had placed us in an overtaking situation.

Once begun on this course, one has to see it through, otherwise one is in the socially awkward position of walking alongside a stranger and looking as if you're trying to join their group.

On we pounded, bidding every yellow-hatted walker 'Good morning!' as we passed.
Even as we eyeballed each of them, we couldn't figure out what they were doing here. 

Finally we reached the foremost group - three young women, clearly fitter than the rest.
'We have to ask. Why the yellow hats?' I gasped.

'Oh,' replied a tall woman. 'It's my hen do and I wanted everyone to come for a walk!'
'What a lovely idea,' I panted.

But, now, having overtaken everybody, it still was not lovely for us. We had not yet reached the top of the ridge and if we slowed down, the yellow-hatted troupe would inexorably overtake us, each one bidding us 'good morning.'

'I think I'm going to die,'  I wheezed.

'You started the overtaking. Now we have to keep going!' grunted Nigel.

Day 6 became the day when we broke our own speed record!