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Tonbridge boss Steve McKimm admitted Dartford's quality finally told on Tuesday night.
Angels produced a spirited defensive display at Princes Park, not dissimilar to the performance that saw them win at Ebbsfleet earlier this season.
But this time Nassim L'Ghoul converted a moment of magic by Jacob Berkeley-Agyepong to break Tonbridge's brave resistance.
"I thought we did very well in the first half, kept them at bay," said McKimm. "Jonny Henly had one save to make and a couple went past the post that didn't trouble him and he had them covered.
"We know what their strengths are and we stopped that at source, with the forwards dropping in. We showed them respect but in terms of we nullified what their threats were for the majority of the first half.
"I wanted that to continue in the second half but for some reason we just dropped deeper and allowed them a bit more space, and with the quality that they've got they are going to hurt you eventually."
McKimm knew it was going to be a tough ask to snatch all three points against a Dartford side who reached the play-offs last season and are eyeing the league title this time around.
He added: "We haven't worked their keeper but they only worked Jonny twice and put one in the net. They are where they are, and we're where we are, I've got no gripes about that. I know what we've got to do.
"To get a draw here or even nick a win would have been a great result for us but they had to win because they're striving for that top spot.
"I'm a realist, and I'm sure Tonbridge supporters don't think I'm being negative in saying that you come to places with what they've got, the resources and their aims to get out of this league, and we've got different aims, and that's to be an established club at this level.
"We've got to do that for the next two or three years before there is any hope of us pushing on. That's not being negative, it's being realistic.
"I buy into that because I'm manager of the club, and that's what the club are telling me. Of course I want promotion and the players want promotion but I've got to look at who we're up against, and establish ourselves as a National South side for two or three seasons before we can dream about getting more revenue in to increase the budget and then to push on for play-offs and promotion."
McKimm praised the efforts of his players, including midfielders Adam Lovett and Zakary Guerfi.
The duo ran out of steam in the second half but there was enough in their display, along with new left-back Tom Henfrey, to give Tonbridge encouragment going forward.
"Maybe that was the reason that we dropped a bit deeper (in the second half), and the reason why we seemed to lose a bit of shape," added McKimm.
"Adam hasn't played competitively for 10 months so to last 75 minutes and give me that energy was superb.
"I thought Zak was brilliant for 70 minutes. He was man-of-the-match in the last game we played, he kept his place and he was really good. He held his hands up and said 'gaffer, I've gone' which is what I want. I don't want people out there trying to be a hero.
"Tom didn't look out of place at left-back as well, and he'll only get better. In general I was pleased with all the players, even the established ones. I felt that we needed a bit more communication as the forwards were dropping deeper, then the midfield, and the back four so it was a knock-on effect. You've got to have a bit of responsibility."