Our triffid

We acquired this plant some years ago, as a succulent just a few inches tall. For many years it hast sat as a rosette by our driveway without doing anything except to grow slowly. Then this year it decided to bolt, and throw up a huge flowering stem.

I've no idea what it is, or whether it will die after this massive reproductive effort.

PS Sorry I've been so abyssmal with comments recently, will try to catch up over the next day or so.