Further promotions ... https://www.gwr.com/your-tickets/ways-to-save/long-weekender

 
Go a stage further - all peaks on all TOCs to be the same - say 0700-0900 & 1630-1830.

Changes from lighter used fare to higher fare to be made at Fare change dates (there are 3, January, May & Sept), not timetable dates

 
I remain of the opinion that three different fares only would be workable.
If a previously lightly used service becomes popular, than the TOC may in future charge the higher fare for that train. TOCs would be allowed to alter this at their discretion but only at timetable changes.
To control the greed of TOCs at least 25% of trains would be required to be "super bargain", mainly very early morning or late night services or rush hour journeys made against the main flow.
And no more than 25% of trains would be allowed to be peak fare.

 
The one thing we *really* don't need is a system like many airlines have, where the fare quoted flexes as the popularity increases or the date of travel rapidly approaches...

 
One problem with a simple, narrow range of fares is that creating "cliff edges" where the fare rises/drops between consecutive trains often makes the cheaper train overcrowded as people decide to change their travel time a little bit. A way round that is to move the cliff edge further into the less popular time band making it less likely many people will shift. Trouble is that ends up with the last pricier train being very quiet so there are complaints that it should have a cheaper fare. A sliding scale with many small steps avoids the problem but leads to inflexibility.

Some sort of pay as you go system with a sliding scale of fares might work, but crucially it needs to be understandable so people can make informed decisions about when to travel, and the financial consequences of catching a different train.  The London scheme doesn't really do that; most people only have a hazy idea that travelling after 09:30 might be cheaper, and awareness of benefits such as cheaper travel early in the morning, or into central London in the evening peak is almost non-existent so it doesn't greatly influence when people travel.  I used to cringe when prospective candidates for Mayor of London promised such things that already existed.  You can look up each specific journey to check based on time of travel but in practice few do.

I'd agree that pricing by time of booking the ticket is very hard to justify, unless advance knowledge of numbers planning to travel is used to adjust capacity by making trains longer/shorter or running reliefs.  I can't see that happening in today's railway for all sorts of reasons.

...and a final thought. There will always need to be some (relatively) cheap tickets valid even on the most overcrowded trains, or someone travelling a long distance will never be able to get a good value fare. A journey from say Newquay to Newcastle at whatever time of day, or day of the week, is pretty much guaranteed to have at least one leg at a busy time of day somewhere en route.

Setting fares is far from straightforward, and simplification is likely to have as many losers as winners.

 

Which on popular times, will immediately make them heavily used & therefore subject again to higher fares.

 
Whilst I can see the attraction of this offer, looking at the broader picture it seems to be another complication added to an already over complex system.

I have long advocated a greatly simplified fares system with only three different fares offered for each long journey, only two fares for local journeys.

Which of these three fares is payable should be determined by how busy the train is expected to be. Not by the time of booking.

No more discounts for hugely popular and overcrowded trains.
No more punitively high fares for walk up travel on lightly used services.

 

This sounds like the British Rail "Weekend return" except that it's a temporary offer from one TOC and not integrated into the national fares and as Graham's pointed out is directional. Hopefully the railway nationally is looking at this as there are a lot of peak time trains carrying mostly fresh air. A friend used to need to travel on a down train in the peak from Reading using weekend returns, her travel costs rose massively when the fare was withdrawn. For a bit she continued to use the same (empty) train, but eventually switched to travelling on a jam packed one on Sunday evening instead.

 

... and to add to previous comment, an interesting piece of levelling up ... great for Londoners wanting a weekend in the countryside, no good for us country folk wanting a weekend in The Smoke.

For people with who live out west, but stay in London during the week, these tickets could be useful to pop home for the weekend.  MPs for example 

... but please bear in mind as you read my comments I'm looking at the technicalities of the new offer and what it provides, nd not taking a "pop" at any particular groups who happen to benefit from it.   In many ways, it does seem to be another layer / option added rather than the holy grail of simplification

 

17:48 Paddington to Chippenham on a Friday - change at Swindon and arrive 19:07
07:31 from Chippenham on Monday morning - change at Swindon and arrive Paddington 08:44 - £69

17:48 Paddington to Melksham on a Friday - change at Swindon and arrive 19:16
07:21 from Melksham on Monday morning - change at Swindon and arrive Paddington 08:44 - £193.80

Yep, think that's worth a split.

 
GWR have introduced 'Long Weekender' return fares from Paddington to the following stations. Out anytime on a Friday or Saturday, return on Monday (Railcard prices in brackets):

Swindon/Chippenham £69 (£45.50)
Bath/Bristol TM/Bristol Parkway £79 (£52.10)
Newport/Cardiff £99 (£65.30)

With there being no time restrictions on these tickets they could be used instead of an Anytime Single during the Friday evening and Monday morning peaks. Quite a saving.

And anyone wanting a long weekend to destinations beyond those above can potentially make quite a saving with split tickets.

https://www.gwr.com/your-tickets/ways-to-save/long-weekender