The Duchess of Cambridge, as Patron of Action on Addiction, is visiting the charity's Hope House treatment centre in Clapham, south London.
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Emergency services were called to the scene in Lossiemouth, Moray, on Saturday morning.
Members of the Rail, Maritime and Transport union on Arriva Rail North (Northern) have walked out for 24 hours.
The train travels the 16 miles through Hong Kong to Shenzhen across the border in China in just 14 minutes.