If there's a forseeable event (bad weather, tube strike etc) that was likely to make people's journey to work longer, do you think:
a) It's the employee's responsibility to be at work at a particular time, so they should leave the house earlier so they'll be more likely to be in on time
b) It's not employee's fault that it takes them longer to get in, so they should just leave home when they normally would and employers should be understanding of the fact that they'll be late
Just a musing really as there's a bit of a difference of opinion in our office!