easy one really,
it was originally fixed so had only a few braze ons,
it was updated for gears and resprayed in the mid 70's using high end components for its previous owner by Bob Jacksons in Leeds.
I didn't want to start getting all the gear braze ons etc removed as they were part of the bikes history
1970's high end components were /are of a better standard and more useable than 1950's stuff IMHO (I have 50's equipped bikes also)
700c's are easier to get decent tyres for than the original 26x 1 1/4"'s that were fitted originally though it did also run on 'continentals' 27"S (700 tubulars)