The overnight ferry from Hook of Holland to Harwich was delayed for two hours on Sunday after three men were caught trying to cross the North Sea illegally.

The three Moroccan nationals were found on board after border police received a tip-off about possible stowaways. Coastguard and harbour police boats were also used to search the waters around the ferry.

Border police spokeswoman Marloes de Ridder said it was not clear how the men had managed to evade detection during routine checks of lorries boarding the vessel. ‘We suspect that they jumped out of a trailer while they were on board,’ she said.

The men are currently being detained while police investigate how they travelled to the port.

The number of people trying to travel illegally from Hook of Holland has increased sharply in recent years. Since the start of 2019 450 people have been intercepted on board ferries, 80 of whom reached port in Harwich. De Ridder said human trafficking gangs were suspected of being behind the increase.