Czechs and Slovaks are to mark the 20th anniversary of the Velvet Revolution – which brought down the Communist government of the then-Czechoslovakia. Past and present students will re-enact a Prague march that started the events.<br/>The Communist Party announced it would relinquish power after hundreds of thousands demonstrated for 12 days.<br/>The dissident playwright Vaclav Havel, who led the revolution before becoming president, is to attend a Prague rock concert as part of the celebrations.<br/>