Ruth Lawrence is a participant in the Amazon EU Associates Programme, an affiliate advertising programme designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.co.uk
If you use this blog for long enough you will notice that there are links to Amazon. Following those links means that if you purchase from Amazon I will get a referral fee, a bit like commission. I've chosen to use Amazon affiliates over other means of advertising because it gives me control of what appears on this blog. For you that means that you don't have to look at adverts that are not relevant to you or this blog.
I hope that explains what is going on, and that you will continue to enjoy reading.