Home page points to another page

Hello, just as I thought I’d cracked it!!!

I have WP Twenty Ten and have created a Child Theme. All has been fine with set-up and modification until today…

I added 2 new pages (using my version of one column template) as child pages to my T-Shirt page.

I have Pretty Permalinks set up so my new pages were set as https://www.myurl/T-shirt/London-Designs and ditto/Windsor-Designs

Unfortunately T-shirts is now my home page!

I niticed something odd in the Permalinks Settings… where I typed a custom URL to specify the Pretty Permalink e.g. https://www.mydomain.com/contact it has changed to /http:/www.mydomain.com/contact – is this correct behaviour?

I have deactivated and reactivated my plugins as I read somewhere that this is a common culprit apart from that I am stuck!