They played almost a full half against 14-men but didn’t have the bite to put their opponents to the sword, and a serious debrief now needs to be conducted into what is going wrong in the nation’s player development pathway.
The result means Scotland finish the delayed championship bottom of the table with zero points after five defeats.
It was a frantic first 20 minutes. Scotland took an early lead through a Cammy Scott offside penalty, but they then coughed up possession at the restart and Wales took advantage when giant blindside Chris Tshiunza barged over.
Scotland hooker Patrick Harrison then went over, only for the pendulum swing right back the other way when Welsh inside-centre Joe Hawkins powered home. Not to be outdone, Scotland inside-centre Michael Gray showed plenty strength of his own when muscling his way to the line, before Welsh loose-head Cameron Jones got in on the act.
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That made it 17-19 to Wales with only 24 minutes played and it looked like a basketball score was on the cards, but the things slowed up and there was no more scoring in the first half.
The Scots got a boost when Welsh flanker Harri Deeves was sent-off for gouging early in the second half, and they initially took advantage when Ben Muncaster rumbled over, but Wales responded superbly, and a ferocious onslaught earned them a penalty-try and a high-tackle yellow-card against Scottish winger Ollie Melville.
Costelow then banged over two long-range penalties to kill the game off.
Scotland: A Clayton; F Callaghan, S King, M Gray (T Glendinning 75), O Meville; C Scott (C Townsend 64), M Redpath (E Cunningham 48); MJones (C Lamberton 41-42, 60), P Harrison (J Drummond 48), C Bowker (G Breese 35), E Ferrie, A Samuel (M Williamson 48), O Leatherbarrow, H Morris (R Tait 53), B Muncaster.