All part of a depot wide review on routes.  Worcester is expanding and Oxford has a fair bit of spare capacity, so it might not be the worst idea in the world as they only cover a handful of trains over the route.  Time will tell.

At present, there's only one empty stock movement from Stoke Gifford to the North Cotswold line in the morning, 3G18 04:42 Stoke Gifford to Great Malvern, which forms 1P18 07:13 Great Malvern to London Paddington. The empty stock is at Shrub Hill at 06:31.

There's two return workings in the evening.

5G36 21:23 Great Malvern to Stoke Gifford (at Shrub Hill at 21:58) is the empty stock from 1W36 18:57 London Paddington to Great Malvern (21:18).
5G29 22:21 Worcester Shrub Hill to Stoke Gifford (23:45) is the empty stock from 1G29 19:36 London Paddington to Worcester Shrub Hill via Stroud.

The two Great Malvern movements would have to be done with the driver doing the 'other' half of the working (back to Stoke Gifford in the morning and out from there in the evening) either 'on the cushions' or in a taxi.

If you're going to expand the establishment of drivers at Worcester, then it makes more sense for this stock to be parked overnight at Shrub Hill.

If you do it that way, then there's one night-time duty for Worcester, taking the 5G36 from Shrub Hill (21:58) to Stoke Gifford (23:40) and  coming back with 3G18 04:42 from Stoke Gifford to Shrub Hill (06:31)

That might well be how they do it, Worcester_Passenger.  Although don't forget Gloucester drivers also sign the route from Worcester to Bristol.

Oxford's second link has signed the North Cotswolds (as far as Malvern Wells) for over twenty years.  With those links growing in numbers over that time it now stands at over 70 drivers - virtually the whole depot - that sign it.

Worcester GWR driver numbers are increasing at a quicker rate than HSS drivers are decreasing.  Originally the depot was 30 HSS drivers.  It is now 22 HSS drivers and 18 GWR ones.  Worcester GWR drivers now sign to Paddington via North and South Cotswolds routes and from Bristol Parkway to Paddington.  They also sign Turbos.

HSS is dying out as people retire, and it's probably no surprise that they are now starting to be starved of route knowledge.  Morale seems to be getting quite low on the HSS side from casual conversations I've had as that fact is slowly dawning on them.

To what extent in the grand scheme of things that will result in additional crew shortages remains to be seen.

Yes - and now it does have a topic of its own. 

CfN.