A group calling itself the IRA has claimed responsibility for suspect packages sent to armed forces recruitment centres last week. Scotland Yard said a group using a recognised codeword had contacted a media outlet in Northern Ireland on Saturday.
Four suspected explosive devices were discovered at Army careers offices in Oxford, Brighton, Canterbury and the Queensmere shopping centre in Slough last Thursday.
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The capital's theatres also generate more searches than those in any other city, according to research by Google.
Union officials are expected to meet next week to plan further stoppages if talks fail to resolve the dispute.
Natalie Sharp and Christine Bicknell appeared in court over an alleged incident at a Lidl superstore in Wallington, south London.