taping at a corporate level didn’t exist until 20 years after the OP’s show aired – and another 20 years until consumer taping entered the picture
even then, BBC had no compunction about continuing to erase stuff – only relatively recently, they’ve started to realize just how bad a decision that was and have been begging for copies from people who taped shows to VHS – which itself hasn’t gone over too well because BBC also has a reputation of prosecuting home tapers, so without a promise of amnesty, no one’s coming forward …