Looking down my chimney

I've had a look down my chimney today! Unusual you might think, wouldn't someone look up a chimney? Well yes, you're right, unless of course you're standing on the roof, then you look down the chimney. Let me explain - today I finished off a little job I started last year, namely the painting of my flat roof dormer on the front of my house. Whilst I was up there I checked my chimney stack and I had a good look down the chimney itself. I was a bit surprised that the chimney wasn't lined (I'd been warned to look out for this on various articles I'd read on the t'interweb) and it also appears never to have been used as an open fire as there's very little dirt in there? Anyway, apart from all that it appears to be sound and I'm planning to sweep it soon - and with this done I can organise my plumber to take out the old gas fire and then start the installation of the new fire back - it's all coming together.