Very interesting. I now understand what happens.

Thank you one and all for the input. It is clear that if photos are accidentally wiped then recovery should be made before the card is used again, as the re-use will overwrite what was there before.

I recently very stupidly wiped a whole load of shots from my computer after I had downloaded them from my Pentax K7 via a card reader and had gone through the formatting of the card in the camera.

I have a recovery programme on my computer which not only recovered the "lost" shots, but also those taken a year or so ago when I used the same card back then (I have quite a number of cards I swap around on a regular basis).

If I had already downloaded the shots from the card and then formatted the card in the camera how could a recovery rogramme recover such so-called erased shots ? Are they in fact in a separate section of the card "for ever" ?

Can anyone let me in on the secret ??