Thanks for your message Alan.
In answer to your questions, the communication received was an email rather than a letter. It came from the Oval Labour email account which has been used to send around newsletters about the councillors’ activities on a number of occasions in the past.
I am satisfied that the email was legitimate. It was received by a number of people I know and the councillors have never denied they sent it. Indeed they are well know supporters of the Smith campaign having sent signed the Labour councillors’ letter in support of him. http://labourlist.org/2016/07/500-labour-councillors-why-we-are-backing-owen-smith-to-continue-the-fight-against-austerity/
With your point about data protection. It is a good one. I for one have never asked to be added to their email list and yet I receive their emails.
A number of friends of mine in Lambeth receive email newsletters from the councillors and have never asked to be added to an email list. It seems like the councillors have a policy of taking any email they find and adding it to their email list. A clear breech of the data protection rules as you say, but I guess their view is that very few people know the data protection rules, and even fewer can be bothered to make a complaint.
You ask why I wrote this a month after receiving it. The answer is really that I am not a Labour member, and was frankly a bit tired of the news being dominated by talk of entryism over the last week by the hard left. I think the issue is a distraction, and as I said in my blog, opponents of Corbyn were obviously playing the same game too!
I find it interesting that Tom Watson finds a fringe socialist group with a couple of hundred members that wants to join Labour to back Corbyn and that makes front page headlines in major national newspapers. But this email was most likely sent to thousands. Many of the people I know who received it didn't even live in their ward!