Magistrate Desmond Nair has returned to court after a brief adjournment, and is outlining the considerations he must take into account when making his decision.
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It is hoped the 7,400-mile journey will become a cost-efficient and time-saving way of boosting trade between China and the UK.
The Prime Minister said Parliament will be given a binding vote on the final deal, but said the result will not stop Britain leaving the EU.
Officials from the train drivers' union Aslef will meet managers from Southern Railway, whilst the RMT will meet separately with Acas.