Thanks to those of you who've explained Swindon's rationale. What you've written, ties in with what I saw there spring 1985; and fills in a couple of gaps in my own understanding.
Two questions from me:
1) what influenced "scrap in-house versus sell for 3rd party disposal"? Class 25s and 27s scrapping included at Swindon Works and at Vic Berry's, Leicester. 33 021 and 33 055 ended life in MC Metals, Glasgow.
2) what influenced how long a BR disposal lingered intact? D818 "Glory" I appreciate was an outlier case; but 84 008 was still in Crewe Works' scrapline in summer 1986.
The mid 1980’s saw a big change in disposal policy, all based around the changes happening at the BREL works. Quite apart from the closures, they were all being downsized as a result of the move to CEM (Cost Effective Maintenance) overhauls.
With the increase in withdrawals and now the capacity to undertake large scale scrapping of locos having been reduced, the large scale reversion to the private sector occurred. Of course, coaches had consistently been going to private sector scrapping locations for decades.
The demise of the regional CM&EE organisations caused a loss of focus on disposals. The BRB actually formed a working group to get it all back working again, prodding the Sectors into action. This group met regularly until the ROSCOs were setup. I was a member of this group as I had previous experience in loco and stock disposals. It was chaired by Tony Smale, the NSE Rolling Stock Manager.
In pre-sector, pre CEM days the CM&EE BRB would decide whether a loco would be scrapped at BREL or put out to tender (by Derby) for sale. The Regional Shopping Bureau would organise any move. Presumably, the CM&EE BRB and the BREL management would know what capacity existed at each works for this activity.
Locos tended to linger at main works if bits were going to be needed in future but sometimes until a few locos were collected, it wasn’t economic to set a gang on them. A good example of the former was steam engine 5815 which was withdrawn in 1961 but its boiler was still in stock as a spare. So the loco lingered at Swindon Works until the boiler was finally withdrawn and the still complete loco was then sold for scrap in 1964.