McEwan starred as Lucia in the delightful "Mapp and Lucia" series in the mid-1980s. It's out on DVD now and I highly recommend you snatch it up immediately before it goes out of print. It's one of the very best British comedies ever.
In the series, McEwan establishes what I consider to be the definitive version of Lucia. She is so delightful that as soon as I found out her readings of two of the Lucia books had also been recorded, I bought them -- although I had never purchased books on tape/CD before.
Suffice it so say, I was not disappointed. McEwan is a wonderful reader who brings out all the wit of the books, and I can't stress enough how marvelous it is to hear her once again using her "Lucia voice."
This has my highest recommendation.