At the risk of steering this in a new direction what interests me about this thread is that it exhibits what I think of as "Engineering Leadership", as distinct from "Market driven Leadership". Interesting because British Rail itself had this same dilemma in the seventies and eighties, and indeed almost every preserved railway when it first started out was Engineering-led and Engineering thought, albeit unconsciously. And in every single instance without exception it failed. It failed when each railway came to recognise that diversification, new markets, separation of markets, and repeat business were the only routes to survival, let alone success. This was when General Managers from outside the hierarchy came to be appointed, Santa Specials, Catering trains, Thomas, Ivor and the rest came into being.
The enthusiast market is being underestimated and misjudged here because it is being regarded as an absolute statistic and not analysed for underlying characteristics. Just for starters the enthusiast market has greater distance independence. Secondly it is resilient for repeat visits. Thirdly it is loyal to the movement as a whole. I could even go on to analyse the disposable income characteristics of the enthusiast market but I'm sure you can imagine the demographic characteristics by observing how many families go on heritage diesel raitours
Technical challenges are there to be overcome. I repeat again that I have yet to see a properly conducted cost benefit or market analysis of the potential for selective higher speed running. My basic market propostion is that
1) the great lure of higher speed running is to allow preserved engines to work harder, not necessarily to shorten journey times.
2) Higher speed running on a preserved line offers visitors the chance to see and experience the engines at work from multiple vantage points inside and outside the train. You can travel on a railtour and not enjoy the variety of locomotive experiences from a day on a suitable provisioned railway. In fact they are complementary experiences.
3) The characteristics of the enthusiast market mean that the income stream is more certain - unlike huge investments made for the benefit of the casual visitor markets.
4) The characteristics of the enthusiast market mean that it is possible to greatly increase both numbers and ratios by offering it a new experience. (eg Tornado)
5) Freight train weekends are an example of an operation aimed solely at the enthusiast market and would not exist if railways took the statistical approach outlined by others above. That is not the way to do business. Railways still cater profitably for enthusiasts even though they form less than 5% of annual passenger figures, because they are concentrated on some weekends when that proportion is reversed.
You can probably tell I'm a consultant by trade as well as an enthusiast by choice, and the preserved railway movement can and must do a whole lot more if it is to fuel the kind of ambitions that many of us still dream about yet dare not utter.