Dash of Spice outdoes Murray's mighty effort

Cardiff Blues 11 northampton 5

So there will be an aptly Anglo-Welsh final to this competition, which may bite the dust or return in a different guise next season, depending on who wins an argument among the unions and clubs. Cardiff Blues won the second semi-final of yesterday's double-header by making better use of the kick for position than Wales have done of late and warding off a Northampton performance in the tight which enhanced the reputation of their putative Lions prop, Euan Murray.

This was a partial rebirth of the Blues after having so many players away during the Six Nations, and they appeared readier for action than the Ospreys had been in the first semi-final. Time is short for fringe Lions candidates such as Northampton's Ben Foden, whose versatility, covering full-back and scrum-half, is a virtue. Foden wore the No 15 here and quickly got used to tracking well-placed Blues punts into all corners of Coventry. Foden's frustration was ratcheted up in the closing play of the first half. Northampton attacked right then left, and though Stephen Myler chipped deftly over the cover, Foden and Paul Diggin got in each other's way as they gave chase.

Both Blues half-backs here are joining English clubs next season – Nicky Robinson will be with Gloucester and Jason Spice at Bristol – and it was the New Zealander Spice who nipped over for his side's only try, in the 33rd minute. The Saints defence was forced back by Maama Molitika, Jamie Roberts and Leigh Halfpenny and Spice finished when his opposite number, Lee Dickson, left a gap at the side of a ruck. Ben Blair missed the conversion but his second-minute penalty made for a lead of 8-0.

The Blues had their struggles at the breakdown, where the injured Martyn Williams would normally have been foraging. Foden, meanwhile, may have been lifted by the public address playing a half-time track by The Saturdays, among whose number is his girlfriend, Una. Whatever the case, the full-back's garryowen at the start of the second half drew a knock-on from Xavier Rush. From the scrum, followed by a ruck, Myler broke a tackle and the centre Joe Ansbro batted off Halfpenny to score at the left-hand corner.

Flying breaks by the Blues' wings, Halfpenny and Tom James, raised the tempo; there was a penalty when the Saints stood up on the loosehead side, but Blair missed and the lead remained 8-5. It must have made Murray even keener to get one over Wales's Gethin Jenkins opposite him, and the Scot and his friends were happier on the hour, rattling forward to earn a penalty. But Barry Everitt, just on for Myler, missed from 40 metres. Much the same happened soon after – though, bafflingly, the Irish referee, George Clancy, ruled that the backpedalling Blues' had managed to wheel the scrum – as Murray kept up the pressure.

The score went unchanged until Blair's 71st-minute penalty, when Northampton failed to roll away at a tackle. That was enough to ensure the Blues' passage to Twickenham on 18 April. No Cardiff side have played there since the Middlesex Sevens of 1946.

Cardiff Blues: B Blair; L Halfpenny, T Shanklin, J Roberts, T James; N Robinson, J Spice; G Jenkins, G Williams (R Thomas, 61), T Filise (J Yapp, 66), D Jones (B Davies, 55), P Tito (capt), M Molitika, X Rush (S Morgan, 76), R Sowden-Taylor.

Northampton: B Foden; P Diggin, J Ansbro, J Downey, B Reihana (capt); S Myler (B Everitt, 59), L Dickson (A Dickens, 69); T Smith (S Tonga'uiha, 48), D Hartley, E Murray, I Fernandez Lobbe (M Easter, 69), J Kruger, N Best, R Wilson, S Gray (C Lawes, 65).

Referee: G Clancy (Ireland).