On Sunday, Rwanda’s foreign minister said his country was in “early stage” talks with the Trump administration about a deal to take in migrants deported from the United States.

That news had a familiar ring in Britain, where the former Conservative-led government agreed to a deal in 2022 to permanently deport asylum seekers to Rwanda, then spent two years and hundreds of millions of pounds trying — largely fruitlessly — to make the plan happen.

When Britain’s highest court ruled that the proposal broke human rights law, the Conservative government tried to use new legislation to override the judgment. But in the end, the policy proved an almost complete failure, and the new Labour government, which was elected last year, scrapped it, citing its huge expense and unworkability.

Here are some lessons the British debacle may hold for the Trump administration.

It could be expensive.

The British government spent 715 million pounds, about $955 million, on the plan, which it claimed would deter illegal migration.

As well as £290 million paid directly to the Rwandan government, millions more went on preparing deportation flights, readying detention centers and I.T. systems, and paying for staffing and legal costs. But in the end, only four migrants ended up being sent to Rwanda — and they went voluntarily and were paid £3,000 each to do so.

Official documents show that the figures were a small fraction of what would have been spent if the deal had been fully carried out. The British government had agreed to pay Rwanda £150,000 for every person deported, a sum that would pay for a five-year “integration package” of accommodation, food, medical services and education.