You could try this for stripping varnish just be careful, use rubber gloves and safety glasses.
Go to your local supermarket and get a can of lye. Over here Gillets is the brand I use, costs around $2 a can. Years ago people used to use it to make soap, I guess it is still used for cleaning or something. Anyway dissolve the lye in warm water in a quart glass jar. Don't use an aluminum container. It will eat it. Paint the solution on the varnish using a natural bristle brush. It eats plastic too. Wait a few minutes and wash it off with water. Let the wood dry and sand down the raised grain. Proceed with staining. The nice thing with lye is that it works very well on varnishes and also bleaches the old stain out of the wood as well. It is also great for aging cherry wood.
Thanks for that, on another board someone suggested,
" Its is called scrumble/scrumbling, and it was applied to make the wood look better than it really was, the easiest way for you to remove it is to apply stripper liberally and then cover/seal it over with polythene or cling film, this will stop the stripper evaporating and the stripper will work longer and strike deeper, leave it at least a couple of hours to get the best out of it. When you remove the cover scrape or wire wool any thing that is left and wash down with WASHING soda to neutralise the stripper and carry on to sand it down when its dried. "
The method I use I want the wood to match the sanded down doors, rest of staircase etc. Probably I could get a nice effect by staining the treads steps on the stairs whatever they are called. If I can get the wood cleaned and sanded down so the wood has a uniform bare wood colour. Should be quite easy to stain might be able to close match the stain so looks like doors. Don't really know what do you and others think?
When you say, " Wait a few minutes and wash it off with water" Do you mean just wipe over with a wet cloth, sorry to be dense, can elaborate explain the technique please?