The nine-year-olds were on 'work experience, but anyone who unwittingly wandered in for their post could easily be forgiven for thinking they had stumbled on a frantic episode of the Generation Game.
After teaching the group to grade the outgoing post while also saving fingers from being jammed permanently in the franking machine, Mr Morris handed the children over to his supervisor, Peter Cooper.
Not that there would be any respite for him - there were another six pupils due soon.
'Look sharp, we've got this lot to deliver,' said Mr Cooper, setting off with his small entourage, loaded with parcels and big brown envelopes.
Three floors later, having interrupted a top-level meeting with cheerful bellows of 'hello and waving at countless well groomed secretaries, they went down to the security rooms.
'There's pounds 15,000 in that petty cash safe. If you can open it you can have it,' joked the security man.
Half a dozen determined hands set to work twisting the combination lock, doomed to inevitable failure.
Class B had been split into four groups of six, each group visiting different departments on a break-neck schedule. The day before Class 5S had had the privilege.
The departments visited included accounts, to learn how to check invoices and write cheques.
In advertising, they designed a mock advertisement for biscuits. They also drew up employee pensions schemes and grilled staff with a quintessential question: 'How much do you earn?'
Some pupils were as impressed with the decorations as the work stations. 'I never expected to see so much gold, even gold light switches in the toilets,' said one.
Once in Information Systems (the computer room) a reverential silence descended over each group. Here the pupils were introduced to CD videos, video telephones and computers which translated English into Japanese automatically.
The silence was broken only by amazed whispers of 'wicked. Each group had to be cajoled and coaxed to leave the computer room - they still had mock press releases to write in the boardroom before tucking into a VIP lunch.
For one girl this was not good enough.
On a press release that was headlined 'Sunny Nicola goes to Grand Met she wrote: 'I came to Grand Met because I wanted to learn all about the computers. Instead they gave me biscuits and sat me in a meeting room.Reuse content