Replacements (used): Daniel Suter (Ospreys) for Thyer 4; Calum Lewis (Blues) for Suter 59; Sion Bennett (Scarlets) for Ieuan Jones 68
Unused: Evan Yardley (Ospreys), Daniel Suter (Ospreys), Lewis Young (Blues), Alex Schwarz (RGC), Rhys Patchell (Blues), Owen Jenkins (Blues)
That lead was increased to 34-17 when Blues centre Cory Allen snapped up an interception try after 47 minutes, but that was the end of the Welsh scoring. From then on the English gradually worked their way back into the contest and three converted tries before the end of a classic contest put them into the final against Ireland.
Wales had a disastrous start as they conceded a try in the first minute to England full back Jack Nowell. Outside half Harry Slade.added the conversion and then a penalty on 13 minutes.
The Welsh cause wasn't helped when they lost Blues tight head prop Brad Thyer after only four minutes with a badly cut mouth, but they slowly worked their way back into the contest and by half-time held the upper hand.
Blues wing Harry Robinson, who has been capped at Under 20 level this season, stopped the rot with a try midway through the first period and Ospreys outside half Sam Davies converted.
Davies then converted a second welsh try from Robinson's wing partner Jake Randall and then kicked two penalties to give his side a 10 point lead. Three minutes into the second half full back Jordan Williams waltzed over for a third try and Davies' conversion made it 25 unanswered points.
The English riposte came via tight head prop Dan Herriot, who trundled over for his side's second try, which Slade converted. That launched a tit-for-tat try fest as Wales centre Corry Allen responded with an interception score three minutes later.
Davies hoisted his match tally to 14 with his fourth successful conversion, but that was the end of the Welsh scoring. Over the remaining 23 minutes England picked up where they had began to mount a major recovery.
Full back Nowell ran in his second try and then centre Mark Jennings crossed with seven minutes left to play. Replacement outside half Will Hooley converted both to cut the deficit to a mere three points at 34-31.
It looked as though Wales would hold out when back row man Dan Thomas forced a penalty which Wales were able to kick to touch as the final seconds ticked away. But England stole the line-out and mounted one last attack that ended with wing Tony Watson stealing the headlines and the glory for his side.
His try was converted by Hooley and England booked their ticket into the final with the most dramatic of revivals.