The gardener swore on the bible that she had not mixed up the plants or planted a different cultivar in it’s place.
Hello Cecily. I don’t think she lied. You say that the plants were moved in 2016 and the picture you took of the semi-double paler flower was made in 2017. That’s thus the first year after moving the plant. It’s not unusual for a peony to have slightly different flowers the first year after moving it. Usually this means that you have a less double flower (or sometimes single) instead of the normal double one. The color can change a bit as well, although you should not see a red or white flower of course. But the paler pink would not be unusual for me. I’d expect the plant to give the usual double darker pink flowers from the second year on, which would be this season. If your plant gives you a good amount of stems and flowers, then your Alexander Fleming will have returned. If however in the coming season all you get are the same pale pink semi-double flowers, then it might be another variety, although nearly impossible to tell which one (there are a huge number of pink doubles available). Also take into account the foliage (dark green with this cultivar) and the shape of the bush (stems standing straight up for Alexander Fleming) to compare.
But I’m pretty sure that it will turn out to be Alexander Fleming.
All the best,