Strictly speaking nesting tickets is not allowed, but I know people who do it regularly and don't get caught.

I actually think it would be unenforceable if push came to shove, especially if BA.com sold you the tickets - you could argue that BA, having full access to your existing travel plans, could see you were nesting and had the opportunity to refuse to sell you the tickets.

Bottom line - do it, I doubt anything will happen.

BAH