Pre-season friendlies are usually played in summer sunshine - not in Boston - both sides had to contend with monsoon-like conditions at the Jakeman's Community Stadium.
In the end, an early close-range finish from Swedish front man Gustav Lindgren proved the difference between the two sides as Peterborough United continued their preparations for the new Sky Bet League One campaign with a hard-fought 1-0 victory over the Pilgrims.
LINDREN opened the scoring on nine minutes after superb approach play by Brandon Khela, with the Swede's striker finding the back of the net despite the best efforts of Bobby Jones.
Ryan De Havilland saw a shot blocked and Joe Andrews was denied by Jones as Posh pressed for a second goal just after the quarter-hour mark.
Alex Bass kept out a header from Dylan Hill moments later while Declan Frith fired wide at the other end as the end of the first half approached.
Maguire was denied by Bass two minutes after the re-start before Abraham Odoh came close to doubling the lead only to see his powerful effort crack against the crossbar.
Frith and Andrews both fired wide before Trialist C clipped the outside of the post for the hosts as they pushed forward for a late equaliser in vein.
Posh are next in action at Milton Keynes Dons on Tuesday evening.
Boston United: Jones, Kelly, Teale, Mills, Sloggett, Coyle, Hill, Maguire, Donnelly, Lankshear, Richards. Subs used: Lovett, Grist, Scott, Green, Raikhy, Waldock, Ging, Cropper, Bradley, Trialist C.
Posh: Bass, Dornelly, Hughes (sub Claxton 63min), Mendonca, Mills, Khela, De Havilland, Odoh, Frith, Andrews, Lindgren. Unused subs: Westcott, Shofowoke, Fox.
Attendance: 1,505