On 25 Mar 2006 13:37:09 -0800, "MIG"
wrote:

The equivalent valid paper tickets would be my travelcard and an
extension ticket, which would not get me in trouble,

They would if you went out of zone without buying the extension first
(e.g. because your plans changed en route).

Having valid tickets for your whole journey but still risking being
penalty-fared is an artefact of Oyster.

I don't think you'd have valid tickets for your whole journey. Your
Travelcard is only valid in its zones, and you need a validated Oyster
card to use pre-pay (which you'd need to go outside them).