Arkle ended up with a bullshit mark of 212 which was due to the way the handicapping was in those days. The handicapping was a complete mess.
The handicapper didn't give Arkle 212. It was Timeform. They would need to come out and say they got it wrong and they're unlikely to do that. The fundamentals of their processes probably won't have changed too much, just tweaked or enhanced by computer technology.
People seem to accept that Sea Bird's 145 wasn't a mistake, and that pre-dated Arkle. Only a handful of years later, nobody was arguing that Mill Reef and Brigadier Gerard were 140+ too.
Yet it took a generation for a chaser (Dessie) to get to within 20lbs of Arkle.
You might just as readily argue that Arkle was so far ahead he made the others look so bad they were artificially downrated*.
I do accept there is a difference between handicap form and non-handicap form but since Timeform introduced the method of assessment of ability that awarded horses a numerical figure to denote their ability rankings no one has found a better one.
The conclusion offered in doubting Arkle's rating is that Timeform's Flat ratings have been right for 50 years but their NH ratings haven't.
So Istabraq wasn't really that good either.
The 55lbs to Dessie remark has to be taken in the context in which it was presented. Arkle's best form against the Gold Cup in which Dessie's guts got him home only very narrowly from a 100/1 handicapper.
*Which is what the handicapper appears to have done with Cue Card.
Having done handicapping myself now for decades, it isn't hard to go back and check how accurate your old ratings were. I did it recently with old Galway Blaze who won his Hennessy the year they changed the scale from 0-100 to 0-175. You progress by accepting you got some wrong and work out why, and try not to make the same mistake again.
I'm in the middle of just such a scenario with Native River which I've backed at 20/1 for the RSA as I believe it is by miles the best novice on the scene this season so far and is already good enough to win 9 RSAs out of 10. If by mid-March I'm looking back and saying to myself, "Fvck me, I got that well wrong," I'll take it and move on. Timeform never felt the need to go back and say, "Ha ha, chaps, remember the day we gave Arkle 212? What the fvck were we on that day??!!"