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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Paramedics were on standby outside the police cordon as armed officers stood by the property.
A team of researchers has taken samples from the ten busiest London Underground lines to work out which are the dirtiest.
The action comes on top of an emergency timetable which has seen hundreds of trains a day being axed.