It is the question that has the entire nation guessing.
What time will the post finally hit the doormat today?
Yesterday, postal unions and the Royal Mail were locked in battle over the same issue.
Postmen claim they are expected to walk at a speedy 4mph to keep up with delivery targets set by their bosses.
That is a little over the average adult walking pace of 3.5mph - and the same speed as a canal boat or a travel mobility scooter.
Unions are blaming a new computer system for expecting postmen to deliver an 'unrealistic' amount of letters in too short a time.
The Canadian system, called Pegasus, decides the most logical route for the postmen to deliver the mail on their round, known as a 'walk.'
On average, they have to call at about 400 to 500 addresses every day within a three-and-a-half hour slot.
But the system apparently dictates an average speed of 4mph is needed to do this.
This, insists the Communication Workers' Union, is simply not possible on most of the 66,500 'walks' in Britain.
A delivery round rarely involves straightforward walking.
It takes in anything from negotiating winding garden paths to a long wait for a customer to sign for a recorded delivery. Keeping up 4mph for three and a half hours would make the pressure even greater.
The Royal Mail insists the 4mph claim is 'complete nonsense'.
'The speed at which we ask our postmen and women to walk is around 2mph and the systems we use to help us plan the most effective delivery walks are used in many other countries,' a spokesman said.
'Royal Mail carefully plans every postman and postwoman's walk so that no one is asked to cover a greater distance or deliver more mail than they are capable of doing.'
But the CWU claims to have been 'inundated' with complaints from postmen who are trying, but failing, to keep up a pace which would make a fitness instructor struggle.
It also claimed to have seen slides from a presentation given by Royal Mail managers which refer to a walking speed of 6.44 or 6.19 kilometres per hour, or 4mph.
Is that a first ? 