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Known as the double contribution convention, this means people on short-term visas will not make social security payments in both the country they work in, and their home country, when working abroad.

But it does includes a three-year exemption on the social security paid by Indian employees working in the UK, on short-term visas.

Inhaling large amounts of zinc or zinc dust can cause a short-term disease called metal-fume fever.

"When people returned, they adapted to short-term gains like charcoal burning."

Estyn said there were several examples of colleges promoting positive behaviour but short-term funding limited their ability to "embed consistent policies, retain experienced staff, and build long-term support structures".