It was before my time, but some British stations broadcast on AM from ships outside of territorial waters in the North Sea to get around strict broadcasting reg

It was before my time, but some British stations broadcast on AM from ships outside of territorial waters in the North Sea to get around strict broadcasting regulations (it was a state monopoly for a long time). They had no choice but to use medium wave because they needed the long range propagation. Some of them were apparently very popular and one of them (Radio Caroline) recently went against the trend of closing AM stations down and re-opened on the old BBC World Service MW channel.