Former Home Secretary Lord Brittan says an allegation of rape against him is "wholly without foundation".
"It is true that I have been questioned by the police about a serious allegation made against me. This allegation is wholly without foundation," he said in a statement.
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The man, in his thirties, was found with stab injuries on the upper deck of a bus in Handsworth, Birmingham, on Monday night.
Thousands of passengers now face delays, with Southeastern trains warning "all services" would be affected.
Paramedics attended a scene in Willesden, north-west London, on Monday afternoon where they found the teenager with stab wounds.