Celtic had their chances, but once again, failed to convert, gifting Lancaster the opener, and losing to a well worked goal.
The opening goal came in the first attack. A hopeful ball forward was not headed clear by Olly Marx, instead flying off to one side, where Thomas Kilifin was suddenly presented with a gift. He still had work to do, lifting the ball over to his striker partner, Charlie Bailey, arriving unchallenged and looking offside to receive the ball one-on-one with Paddy Wharton, who did get something on the close-range shot, but couldn't keep it out.
Celtic were back on terms immediately. Mark Lees back in a Celtic shirt for the first time since 2013, showed remarkable skill to turn Lewis Fenson inside out before lifting an inch-perfect ball to the back post for Neil Kengni to arrive and power a header past Jack Sims.
It looked like Celtic would push on and grab a second when Neil Kengni turned and shot in the box, but was narrowly wide. Kengni provided a great cross for Scott Bakkor to slot home, but Bakkor was an inch away from converting. Daniel Cockerline fired from the edge of the box the wrong side of the post. Liam Tongue latched onto a half-cleared cross, his shot striking Glenn Steel, lifting the ball over Sims, only the crossbar denying Tongue.
Five minutes before the interval, Lancaster broke. Charlie Bailey was given too much space, he picked out Rob Wilson, continuing his run to be picked out by Wilson as he burst into the box, one-on-one with Wharton for the second time, picking his spot and firing into the bottom corner.
Celtic should have been on terms at the interval when Dougie Nyaupembe battled to the touchline and pulled off a cracking cross to the back post. Danny Cockerline was unmarked and perfectly placed, but his header was glancing, not thumping, going wide.
It wasn't until twenty minutes into the second half that Celtic seemed to realise that they were a goal behind. Tongue came closest, hitting the crossbar for the second time in the match, this time from a free kick. Nathan Heath's cross looked for a moment to have been snuck in at the back post by Kengni, but it was the outside of the side netting. At the other end, in rare attacking forays, Luke Jordan twice had chances, but neither time tested Wharton. Right to the final whistle, Celtic looked for an opening, but Kengni and Tongue both squandered opportunities, Kengni scuffing when he needed to strike cleanly, and Tongue trying from forty yards, so in the end, Lancaster's accuracy was what told in the match.