It is interesting how the lifetime of any long-lived organisation soon begins to divide into distinct eras. Governments, companies and newspapers, providing they have a long run at existing, often so neatly split into discreet sections of time half the work of any historian is done for them.
ITV is a case in point. The system as a whole has had many changes and was designed to be flexible over time - if only because those who birthed the baby were unsure of its chances for survival.
1. Competition 1955-1968
The Television Act that created commercial broadcasting in the UK was notable for remaining loose on exactly what the structure of the system was to be. Legislators, bruised and bloodied from the fight just to pass the Act, were happy to leave the details to the new Authority and its first head, Sir Kenneth Clark.
The only really specific injunction laid upon the ITA was for the new network - whatever its form - to be built on the basis of competition. ITV, from the beginning, would not just fight the BBC, but each other - ITV would not be a monopoly.
The system the ITA implemented ensured this. Weekend-only companies fought against weekday ones for regional advertising. Large companies did deals with smaller companies for sales of programmes. The contractors knew the facts - kill or be killed.
2. Regionalism 1968-1992
Lord Hill decided that ITV's violent childhood was to end. He remade the system and forced the companies to grow up and work together by sealing each one hermetically within its own region.
With ATV no longer battling ABC and Rediffusion, ABC freed from the fight with Granada and ATV, and Granada concentrated on the area they knew best, a new system of regional companies providing a regional service grew up in areas that previously had been allowed to think themselves 'cosmopolitan'.
Hill's successors took things a stage further. ATV, the unbreakable national company squeeze into the midlands, was forced to become the midlands-orientated Central. An persuasive argument from a newcomer that it could do better in the south than Southern at providing a local service saw the sudden end to the incumbent's position.
By the mid-1980s, regionalism was so strong that the thought of a contract being owned by a company from outside the region was an anathema and never even considered.
3. Consolidation from 1993
The huge change in the fabric of British life in the 1980s eventually affected ITV. A new regulator operating under a new act saw no reason for regionalism or competition.
The 'big is beautiful' philosophy of the 1980s that led to huge national conglomerates merging with other huge national conglomerates to form huge international conglomerates moved into the system.
Companies liable to be too ingrained in the old ways were moved aside, and new, go-getting companies that announced from the outset their aims to takeover - or be taken over by - other ITV companies appeared.
And so it began. Grampian into Scottish. Tyne Tees into Yorkshire into Granada. LWT into Granada. Anglia into Meridian into Granada. And Central, Westcountry and HTV into Carlton.
There is no telling where this era ends - mainly because there is no compelling reason for it to. Indeed, ITV has always been happy in any situation until knocked into a different one by the regulator. And it now has a regulator that appears determined never to put a new face on ITV again.