Complex sentence: Guy Fawkes is also thought to have been put to the rack, since a royal warrant authorising his torture survives, ordering that the "lesser tortures" should be applied to him first, but that if he remained recalcitrant he could be racked.
Split into simpler sentences: Guy Fawkes is also thought to have been put to the rack, since a royal warrant authorising his torture survives. The warrant states that the "lesser tortures" should be applied to him first, but that if he remained recalcitrant he could be racked.