And that set up Newcastle's first appearance in a final since winning the Powergen Cup in 2004.
The RFU insists England players should not be released for the Powergen Cup semi-finals on 4 March.
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But Wales prefer the option of their four sides entering a money-spinning, revamped Powergen Cup alongside the top 12 English teams.
Standing in the way of a first trophy since the Powergen Cup win against Sale in 2004 are Bryan Redpath's Gloucester.
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The former prop lifted the Powergen Cup the last time Leeds were at Twickenham back in 2005 when they beat Bath 20-13.
In eight seasons with Saints, Smith has played in two Powergen Cup finals, a Heineken Cup semi-final and three Heineken Cup quarter finals.
Ibanez, who won the Powergen Cup, Heineken Cup and Guinness Premiership while at Adams Park, suffered his initial concussion against Worcester Warriors in September 2008.
England fly-half Cipriani was 17 years and 47 days old when he first played for Wasps at Bristol in the Powergen Cup in December 2004.
In 2002 he moved on to Leeds Tykes where he had further success as they lifted the Powergen Cup at Twickenham with victory over Sale in 2005.
Eighteen years later the club has become the first dual-code rugby partnership with Leeds Rhinos under the umbrella of Leeds Rugby, won the Powergen Cup and played in the Heineken Cup.
Dowd won 59 caps for the All Blacks and as a coach with Wasps, helped the club to the then Powergen Cup last year and a second Heineken Cup victory this May.
The 27-year-old graduated from the club's academy, scored the winning try in 2004's Powergen Cup defeat of Sale at Twickenham and is the current captain of the Falcons and the England Saxons side.
The former England A international captained Leeds to their first ever promotion to the Premiership and also lifted the Powergen Cup at Twickenham in the absence of then skipper Iain Balshaw, who had been injured in the final.
Leeds Rhinos will play London Broncos and Wakefield will play Widnes in the two all-Super League ties in the fifth round of the Powergen Challenge Cup.
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