Have alias that never appears in history?

Question

I have a command I never want to accidentally run but I may run it every few days. I have an alias for it alias=' echo my expensive command'. I have HISTCONTROL=ignoreboth on so if I have a space before the command it won't save in my history and so far it's been fine but I suspect I'll accidentally forget to lead with a space. Is there a way to make it so it will never be in the history? Bash is my current shell