The Celtic chief executive lavished praise on Lennon for leading a team in transition into the lucrative competition just as he was watching three key stars head out the door.
Celtic navigated three qualifiers for the first time to join the Champions League elite despite losing Victor Wanyama, Kelvin Wilson and strike star Gary Hooper.
"It really would be very close to Neil's best achievement," he said. "It was a time of transition, we lost some very important players and we had six games to get through.
"We were trying to strengthen and we had some very difficult ties at a very early stage of the season.
"The Q2 games start very early so in terms of preparation and getting the squad right to go to some very difficult places is an outstanding achievement.”
Lawwell knows Lennon’s stock is always rising so long as he is holding his own in Europe.
But the Parkhead powerbroker revealed a plan B is already in place to find a successor should the day come when Lennon is lured away.
He said: “Neil has done a fantastic job and if he continues to progress – he’s still a young manager – I’m sure he will be courted at some point.
“We need to accept that – and I actually take a lot of pleasure in that, for him and for us – and plan for the succession. Hopefully he’s here for the rest of his career."
Meanwhile, Lawwell is satisfied the squad Lennon has at his disposal is good enough to compete at the top level – despite some flak levelled at the Celtic board for not bringing in a marquee signing this summer in the wake of successful financial figures.
With Georgios Samaras and Joe Ledley currently in negotiations to extend their stay at the club, Lawwell was keen to underline just exactly what the Parkhead side can offer.
“We have a great pool and they have access to Champions League football here,” he said.
“When some guys leave here they do miss it. Even going to the English Premier League some-times doesn’t make up for what they have here.”
Mikael Lustig is another who is in negotiation over an extended deal.