[gmueckl]

The BBC did that to save money for new magnetic tape used for archiving. They thought that parts of their archives were just not valuable enough to preserve and chise to overwrite them instead. Unfortunately, some of the overwritten material turned out to be much more interesting and valuable in retrospect, for example a host of Doctor Who episodes which are now lost completely.

[waqf]

Context that's often forgotten here is that the BBC typically didn't even have the contractual right to rebroadcast these programmes (the actors' union would have stipulated a maximum number of broadcasts, for example two within 7 days).

And video releases weren't yet a thing even if the rights could have been secured, so the apparent value of these archives was minimal.

https://en.wikipedia.org/wiki/Wiping#Rights

[benj111]

Your link states

"Talent unions were highly suspicious of the threat to new work if programmes were repeated; indeed, before 1955 Equity insisted that any telerecording made (of a repeat performance) could only "be viewed privately" on BBC premises and not transmitted"

I'm trying to work out if there's a misunderstanding here, as this only applies to repeat performances, not presumably the original performance. So I wonder if recording at all at that time was not standard practise. I tried to work out in what circumstances telerecording was actually used for at that time, havent found much, but found this interesting white paper on recording the Queens coronation.

https://www.bbc.co.uk/rd/publications/rdreport_1955_02

[waqf]

I believe what you're implying is correct. The original mental model of television was that it's live by definition (otherwise it's just an inferior and unduly complex substitute for ciné film, which was well established technology).

So telerecording was just a weird hack, and for a repeat performance you would expect to bring the actors into the studio again.