The bulk of its current demand is flows between roughly Berkhamsted and Streatham Common to Shepherds Bush, with a bit of MK/Croydon commuter traffic at the extremities.
Not quite. Except in the "high peak", these trains tend to be almost completely empty north of Watford. There's actually a compelling argument for only peak time services to go north of Watford Junction.
During the busiest parts of the peaks, there's a healthy flow all the way from Bletchley to about Balham (with different commutes overlapping with each other - few people do anything like the whole journey, but there are still plenty of people heading from the WCML as far south as Clapham Junction, and a reasonable number changing there for the second or third leg of a long-distance commute).
The busiest section of the route, by a long long way, is Clapham Junction to Shepherds Bush. It's quite noticeable how many people use Southern's "Shepherds Bush shuttles" in their own right. As these are 8 coach extra trains against the ARL / London Overground base timetable on the West London Line, they're pretty attractive to a lot of people. The 5 coach Overground trains are something of a miserable experience at most time of day, as they are woefully overcrowded.
Sounds like the sort of service that would be prime for London Overground to operate, albeit MK is a touch too far north for them
It's not really LO, as the service north of Wembley Central takes on a skip-stop pattern which is more reminiscent of fast regional services. None of the services are really frequent enough to pass for a metro service in and of themselves, either.
It doesn't really fit neatly within any TOC. Within GTR, it's Southern, but you could even argue it as a western branch of Thameslink, as they connect at East Croydon. Even if it doesn't reach Gatwick or Brighton any more.
It's a useful addition for some local frequency, where packed terminals don't allow any more services - and a similar frequency augmentation to the WLL, but it really came into its own when Shepherds Bush opened. And of course, connectivity into Clapham, and from South London up to Watford.
It would definitely be better as a regular 2tph service, even if one turned at Watford Junction.
Agreed with all the above.
I always felt that this service should be branded as a “Thameslink West” service as it has more in common with Thameslink than either, Southern, LO and LNWR
This is indeed the unacknowledged counterpart to the Thameslink Core routes, with the added advantages that it is politically quite boring and reasonably reliable as of now. What it emphatically does not need to become is overhyped and the latest magical breakthrough, as it is simply a really good workhorse for the amount of investment it's had.