Career
He took part in the 1920 Summer Olympics, organized in his native county, and in the 1924 Summer Olympics. In the 1920 doubles event Lammens partnered with Jean Washer. They defeated Sune Malström and Carl-Eric von Braun in the first round but lost in the second round in straight sets to the Japanese pair Ichiya Kumagae and Seiichiro Kashio.
At the 1924 Summer Olympics Lammens competed in the singles and doubles events.
In the singles he had a bye in the first round and lost in straight sets to Pavel Macenauer in the second, winning just a single game. With compatriot Joseph Halot he had a bye in the first round of the doubles event but lost in the second round to the French team of René Lacoste and Jean Borotra.