Luton has the step climb and quite a few turns and various legs that can all happen a bit quickly for those not familiar and who let the speed rush away a bit but aircraft are cleared on the SID and are required to follow the SID vertical profile with no local non-standard revisions.
The problem is that
day 1 - Luton - stepped climb - follow the steps or there will be big trouble
day 2 - City - stepped climb - don't follow the steps because if you do there will be trouble.
day 3 - Northolt - stepped climb - follow the steps or there will be trouble.
Now which is the odd one out?