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I think if people knew that on arrival here they were going to be sent straight to Africa they would be less inclined to pay the several thousands of pounds it costs them to get here. A couple of boatloads taken straight onto planes bound for Rwanda and they would soon get the message. (I read this morning that there's a new service from Calais to the Kent coast being advertised on TikTok. A speedboat providing a crossing that takes just 45 minutes. Cost £7,000).
The alternative is to make this country less attractive to people coming here illegally. They're coming from tatty tents in a muddy field in France but they get here, they're fed and watered, they're accommodated in hotels, and they get, free of charge, any medical treatment they may need. Perhaps instead of giving money to the French we should take a lesson from them.