England entered the match as firm favourites after crushing Wales 43-12 at the Gnoll in March but it was the underdogs who barked the most throughout in an intriguing contest played in hail and driving wind and rain.
Blindside flanker Tom Phillips gave a towering performance putting in some big hits in defence and gaining the hard yards in attack while the engine room turned the tables on the England pack after the Gnoll defeat - Wales clearly held the ascendancy in the scrums while the pack generally had the better of the opposition throughout in testing conditions.
Prop Jack Stanley's early try had given England a 5-0 lead, but Wales hit back with three penalties to make it 9-5 through fly half Jarrod Evans before England pivot Theo Brophy Clews reduced the deficit to 9-8 before the break.
Terrible conditions prevented any further additions with Wales' tenacious defence repelling everything England through at them - until five minutes before the final whistle when Mallinder stepped up to send his kick between the posts from half way.
Wales team manager Will Thomas was full of praise for his side despite the gut wrenching defeat.
"In the first half we probably edged it and managed to stay in front by scoring points every time we reached their 22," he said. "We held on bravely in the second half and turned them over regularly to get out of danger so it's really disappointing to lose it in the dying stages.
"Saying that, the boys have put in a vast improvement from a few weeks ago when England dominated us at the Gnoll.
"It's about the journey and the development as well as the results and this team have made huge strides in camp and it shows the effort the coaches and backroom staff have put in.
"We now go in the 3rd/4th play-off match against France on Saturday with plenty of confidence where we will be looking to overturn the 18-17 defeat we suffered against them in Chartres in March," he added.