By Vivian White
Postal workers say they are being asked to carry more packages
We have seen what the mail business looks like: and it is awesome.
Negotiate a few tricky back-flips from the M23 behind Gatwick Airport, and you find the Gatwick Mail Centre.
It is a huge industrial palace for moving the mail measuring 6,000 square metres and employing 650 people at any given time. The Mail, it seems, never stops.
The centre handles 3 million items every 24 hours.
We watched in awe as giant processing machines engorged, shuffled, shook, and stacked endless envelopes - and Royal Mail people tossed and popped parcels continuously into bags.
It was tiring just to watch the volume of activity.
But appearances, it seems, can be deceptive.
The sheer mass of mail and the human energy being expended moving it conceals a tectonic shift in this old business.
When did you last write a letter? Yes, a letter.
What they call in 'mailspeak' a Granny Smith, as in 'Dear Granny, Thank you very much for the brilliant present. It was lovely seeing you again."
Well maybe your Granny is still getting hers, but e-mails are taking over from mail with stamps on them. Royal Mail say the overall volume of business they are getting is going down by 10% a year.
The internet offers one big consolation for the Post Office - parcels ordered over the internet are booming. But the number of parcels gained does not make up for the letters - and revenue - lost.
At Christmas, of course, business booms and we send each other cards. But it comes but once a once a year and then the decline resumes.
And if you are a postal worker, here is the rub. Parcels are heavier, more fiddly to sort, harder to mechanise and to squeeze into that last stage in local delivery offices where postal workers get their rounds ready.
When they do their rounds, the number of letters may well be sharply down but the weight is not - and parcels take longer to deliver.
There is a very real temptation to not wait too long at the door, but instead to drop one of those 'While You Were Out Cards' and continue on your route. Can it be true? Would they?
'In' not 'Out'
Yes they would, consumers say, steam coming out of their ears.
While most consumers surveyed by ICM for Consumer Focus said they thought the Royal Mail provided a good service, 55% said that in the last year they had received one of those cards when they were, in fact, at home 'In' not 'Out'.
Nearly a quarter said it had happened three times or more. The Royal Mail accept it has happened and say it shouldn't.
The Post Office says the business must become more efficient
Beyond the parcel issue, the Royal Mail has a huge management task to reorganise its business - a reality based simply on our drastically changed postal habits.
At the same time the Royal Mail has lost its monopoly on the letter business.
Rivals are competing to collect the mail, but for the moment at least, they're not competing to do the rest, namely the fiddly bits, the sorting, getting it ready to be delivered to our front doors.
Couriers such as DHL and TNT deliver their mail at the Gatwick sorting centre, it is the local postal worker who carries it "the final mile".
This is called "downstream access" officially and as you can imagine, all sorts of other things, unofficially, by aggrieved Royal Mail staff.
Royal Mail still has - uniquely - a "universal service obligation" to collect and deliver at the same price to every address in the country.
Expectations are high of a well-oiled, well-managed business ready to face its challenges, not to mention sound industrial relations and a well motivated workforce.
As most people in Britain have learned in recent months thanks to a string of local and then national strikes, that is not the case. And despite a return to talks, there is little reason for optimism.
In researching the ins and out of the Royal Mail, we met charming and hard-working managers, and postmen and women; yet we were still left in no doubt that management and its workforce are often oceans apart.
Lord Sawyer, who reported on the gulf between them nearly 10 years ago, says little has changed.
"The Royal Mail are going to be the last people who move forward into modern times from an industrial relations point of view," he said.
Panorama: Can't Deliver, Won't Deliver, BBC One, Monday, 14 December at 8.30pm.