Name that couplet??

[Chicklet]

While the light lasts I shall remember
And in the darkness I shall not forget.


Anyone know if this is "known" (...Wilfred Owen ???) or possibly just something I have remembered from a Jed Bartlett speech in West Wing?

[Graham]

It is known. There is an Agatha Christie short story While the light lasts in which this appears, but it's not clear whether she was quoting an earlier work.