I think it was all Beeching. The West Coast had been recently electrified, so the Paddington - Snow Hill service was being shut down as people were travelling between Euston and New Street instead. The line didnt need to be four tracked any more, so they mothballed it. It could do with being back now, but I cant see it happening any time soon. Some of the trackbed is still in place, but some of it is now under tarmac and being used as railway station car parking. Widney Manor and Acocks Green spring to mind instantly.