Recording of a running program with the previous 30 minutes

[gideon_friedmann]

One nice feature of the Tivo is that it keeps 30 minutes of recording on the current channel, so that if I turn the TV on, and find an interesting program running, I can rewind up to 30 minutes.

The question is, how can I record the rest of the program (including as much as possible from the beginning), if I want to keep it on the Tivo. Pressing the record button erases the buffered 30 minutes (similarly if I do manual record) no matter where I am in the viewing of the program.
(I would have expected the TiVo to be smarter about this, or at least to give me the option).

Gideon.