Complex sentence: The press had mocked earlier meetings of working men because of their ragged, dirty appearance and disorganised conduct but the organisers were determined that those attending the St Peter's Field meeting would be neatly turned out and march to the event in good order.
Split into simpler sentences: The press had frequently mocked previous meetings of working men because of their ragged, dirty appearance and disorganised conduct. The organisers were determined that those attending the meeting at St Peter's Field would be neatly turned out and would march to the event in good order.