Apple tree with canker?

[Smews night]

Hi, we just joined the forum as we need advice. We live in London, UK, with an apple tree in our small garden. It has had problems for a while, but now appears to have canker quite badly. Can anybody have a look at our pictures of the tree and tell us if they think it can be saved? We're not gardeners or in the orchard business, so we'd be really grateful of any help. There's a picture of the back of the trunk with bark peeled off, and a picture of the main trunk at ground level showing an area about 2 inches high of no bark. The previous owner planted a rose bush that has grown up through the branches of the tree and is touching/scraping branches at head height. This doesn't seem to be helping. Many thanks.