[akadruid1]

IANAL but the ICO has a readable summary. They say you should be given a simple way to opt out in every communication:

from http://ico.org.uk/concerns/marketing/11

The law says that marketers are allowed to send marketing messages if:

the marketer has obtained your details through a sale or negotiations for a sale (this includes asking for a quote); the messages are about similar products or services offered by the sender; and you were given an opportunity to refuse the marketing when your details were collected and, if you did not refuse, you were given a simple way to opt out in every future communication.

[jack-r-abbit]

To me it sounds like John Lewis met all of those conditions. I can see there might be some grey area in the first one. But I would argue that when the guy signed up on their site, he was at least taking the first step in negotiations for a sale. But it seems John Lewis argued that and lost so I guess I would lose too.

Edit to add: I do think that pre-checked opt-ins are a bit sleazy.