The Minister Without Portfolio struck a chord with a large crowd outside HMV in Queens Street, where Stereophonics were launching a new single, "A Thousand Trees".
The band, from the Cynon Valley, watched while Mr Mandelson autographed posters for the new record. Their leader, Kelly Jones, was moved to promise: "You've got my vote for an assembly. I must say our music isn't particularly political, but Wales needs a voice of its own."
Mr Mandelson's line, "A strong `Yes' vote on 18 September will give the people of Wales the opportunity to develop distinctive policies reflecting their special needs," seemed well-received. The only snag was that most of the hundreds present were under 18 - too young to vote in the 18 September referendum. Jessica Price, a local sixth-former, said: "If I was old enough I suppose I'd vote `Yes'." Then she hurried into the record shop to buy the new offering.
Four 15-year-olds from Cowbridge in the Vale of Glamorgan - an affluent area where off-roaders appear to outnumber Mondeos - were more enthusiastic. "I think it's a pity we don't have an Assembly," Rhodri Williams said. "Actually, I support Plaid Cymru, but on this everyone should get together."
A statue of Aneurin Bevan - a name not much mentioned by New Labour - guards one end of the pedestrianised shopping street. At the other a helter-skelter stood invitingly. Mr Mandelson needed little persuading to ride a coconut mat down the 60ft descent not once, but twice.
Mrs Pauline Smith, a Romany gipsy, then offered to read the ministerial hand and tried to interest its owner in a lucky charm. Mr Mandelson declined both offers.
"He looks like a tall dark stranger to me," said Mrs Smith. "What did you say his name was?"Reuse content