Why does Didcot get more Down HST services (3-4 per hour) than Up HST services (2-3 per hour)

Basically, why do the HSTs from Swansea stop, but the HSTs to Swansea don't stop?

What's wrong with a bit of consistency....

Best guess some clever carriage roster clerk has discovered that if you don't stop the down Swansea you can save a unit over the day.

Up to December 07 at Taplow we had the same on the off peak London Suburban services.

Trains to Padd ran nearly all stations  Oxford to Slough   then Hayes (some Southall) Ealing Broadway.

This was followed by a Reading Twyford Maidenhead Slough most staions to Padd this was formed off the previous down Reading train as below,

Taplow trains from Padd ran Ealing B, Southall Hayes West Drayton Iver? Langley? then Slough and all stations Reading.

This was followed within 5 minutes by a Padd Ealing B Hayes Slough Maidenhead all stations Oxford which formed the up stopper for Taplow Padd a couple of hours later.

Allegedly this save one unit over the whole service. However it made realiablity a nightmare,  if a Taplow stopper was late this made the following OXford stopper late which made it late coming back to Taplow.

You can be too clever running a railway. After all the South Western pioneered regular interval fixed stoppping pattern services on electrification in the early 1900s. They also used to split and divide trains at places like Staines evry half hour. It worked then it still works now the clever bit is getting the stopping pattern right.

Asymmetry doesn't work.

No,

No, it's probably to save an HST set on the Padd - Swansea runs.

The Thames Valley offpeak service is now symmetrical so there is no missing of stops in one direction to save journey time and reduce number of Turbos required.

Ar, I see. It is less of "up trains calling additionally" but more "down trains missing out stops."

Thanks.

Still seems a bit silly - a symmetrical consistent timetable would be better.

But then again, FGW released a leaflet talking about the increase in refreshed HSTs calling at Didcot. In the figures, they quoted the number of trains TO London which (because of the inconsistent timetable, that is the subject of this post) makes it look like just as many return journeys!

Or perhaps demand in is spread a lot more than demand out (less likely, but possible).

Thanks again for giving me some possible answers! 

This some seem possible but probably no, because it is the down Swindon trains that call in addition.

This is really bugging me - and others.

Do any others on this board (who perhaps have more timetable knowledge etc.) know why Didcot has an additional HST (the up Swindon service)?

Thanks.