Complex sentence: Merchant seamen arrived in Cardiff from all over the world, only staying for as long as it took to discharge and reload their ships: consequently many murders and lesser crimes went unsolved and unpunished, the perpetrators having sailed for other ports.
Split into simpler sentences: Merchant seamen arrived in Cardiff from all over the world, only staying for as long as it took to discharge and reload their ships. Consequently many murders and lesser crimes went unsolved and unpunished, the perpetrators having sailed for other ports.