It was actually no problem to lathe the 22,6 mm diameter - used were chisels with hard metal insert.
Choosing a tool with maximum key size seems highly recommendable; by using a 28 mm key size tool there will be just ~ 2,6 mm material left over for the hexagon.
For driving of such a weakened tool it will be advantageous to choose a ring wrench, not a common flat wrench!