In reply to Offwidth:
OtM is the 2nd best guidebook ever written, and everyone interested in Peak District climbing should buy a copy.
Having got that out the way.
Millstone - the map on page 249 shows it directly opposite Lad's Leap. There is indeed a crag there - but it's not Millstone. The map on page 250 shows it at the same level but further west - there's a crag there as well, and that's not Millstone either. The grid reference is spot on though, and luckily (despite the guidebook assurance that the p249 map was all I needed) we had an OS map with us. So we eventually went to the right place, which is 200m south of Lad's Leap, 30m lower (roughly where the 'e' of Millstone is on the p250 map), and out of sight from above.
Slanting Crack: I have the topo in front of me, and it clearly shows it starting up the arete. Yes it's blatantly obvious with hindsight that the routes were swapped. But we believed the guidebook, and assumed that the obvious groove on Cake Buttress must have hidden jugs (it didn't). And yes the name is a give away, but it wouldn't be the only route with a name that doesn't match (Stomach Traverse at Almscliff springs to mind, it used to be a stomach traverse, but for the last few decades has avoided that bit completely). The start of The Arete is also shown wrongly (Martin confirmed this when I queried it). Fair enough about the topo being new - but given that no descriptions are provided for most of the routes, it's especially important to get the topo right.
Regarding timings, I didn't come on board right at the start, but when I did sign up there were still 28 crags without authors (including some relatively popular ones) so presumably only a few months after kick-off. That was February 2010, volume 1 was published about 2 1/2 years later, only a decade or so less than OtM
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