Rugby World Cup winner Matt Dawson has tweeted a picture of himself alongside Olympic rowing star James Cracknell, saying "Here we go. There's no point competing with this fella."
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The three-week trial is designed to speed-up the flow of passengers leaving Holborn station during the morning rush hour.
Tube managers unveiled plans last night to hire a new workforce of part-time drivers in a bid to rescue the 24-hour service.
Masked machete-wielding raiders stormed into a convenience store and threatened the assistant, before stealing cash, cigarettes and alcohol.