The world has long known of this legendary performance, unavailable to the public. I've read that some recordings from dubious sources existed. Now, finally, the official release from the original tapes itself from BBC. Listening to it, I am struck by Klemperer's total command of the score. If you've heard his EMI performance, you may think "it's doctored in the studio". But here is a 'live' performance totally undoctored, thrilling in its intensity, just like the EMI performance. In fact, Klemperer moves faster in this 'live' recording. His finale march and the final chorus for instance, moves at a much faster pace, the effect is quite similar to Solti's Fidelio with Behrens and the Chicago forces, but more intense. Klemperer also makes astute use of the timpani to stunning effect. Hans Hotter was in great voice that night although the voice is a bit woofy. Gottlob Frick is superb as Rocco, his dark bass making him sound authoritative as a father. Jon Vickers is unsurpassed as Florestan. I don't care what people say, nobody does THIS like Vickers. Jurinac is excellent as Leonore. Her high B at the end of her Act 1 aria is slightly messed up but that dpesn't really spoil the overall performance which is beautifully and intensely sung. She has a kind of vibrato which is very pleasing to hear.
The ensemble is not always perfect. There are instances of the singers running ahead of the orchestra. After the trio, at the start of the Act 1 march, the audience clapped hysterically until someone shouted "Quiet! Sssssh!!" because Klemperer did not stop for the applause but continued with the performance even though he was drowned out by clapping. So there are all these warts in the performance, undoctored. But the performance is so moving and intense that it just doesn't matter.
A truly great performance. BTW, I just saw the video from the Met starring Mattila, that is also a great performance. Since Klemperer's EMI Fidelio in 1962, there has not been any truly great recordings of Fidelio coming out. Now suddenly we have 2 together. The 2000 Met production is the greatest Fidelio since Klemperer 1962.