Diamond, who assumed the director of rugby role this week, saw Nick MacLeod and Johnny Leota both score tries in the first half, while Danny Cirpriani kicked nine points.
The Exiles fly-half Ian Humphreys did dispatch three penalties of his own, but helped by Cirpiani’s accurate kicking, the home side clung on to secure their first win of the season.
“The week’s been different – but the coaching team behind the scenes know what they’re doing. The lads paid attention to what we’ve done in the week and we managed to get a hard-fought win,” said Diamond.
“We stuck to the game plan and we played well in the first half.
“We had a shaky start at the start of the second half where we gave the ball away six or seven times through handling errors.
“We’ve managed to get our scrum sorted out to a large extent and our line-out’s effective.”
London Irish director of rugby Brian Smith admitted the Exiles were second best to Sale, although he felt his side had a chance to secure an unlikely comeback before Cipraini cemented the win.
“We lost our discipline and that cost us, but fair play to them, they scored twice against us and we fell off tackles against their power centres a couple of times,” said Smith.
“We believed we could peg them back so we made a tactical change to play with three locks in an attempt to try and squeeze them.
“At 15-9 we looked like we were going to turn things around, but at the end of the day we came away without even a bonus point so we’ve got egg on our face now.”
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BIOGRAPHY: Cesc Fabregas