On Tue, 27 Oct 2009 10:52:12 +0000 (UTC), Tim Woodall wrote:

Only problem I can see is that the detail of the oyster card may be in
his reader. If he still believes, incorrectly, that you are in the
wrong he could possibly cancel the oyster card. If it was registered
you might get a letter with a penalty fare request. Just keep the
ODTC and wait and see what happens

The barriers at the end of his journey probably ate that. (They do at
Watford Junction anyway

That's naughty - they're still valid on the 258.