I agree with Stephen. There is no need for preserver. I've had problems with this before. The idea of a primer is to have it soak into the timber to provide a good key for the following coats.
Preservers, in my experience, can be "oily", likely to throw off further paint coats.
I'm going to upset a few people now by saying that I no longer use conventional undercoat/gloss type coatings. There are plenty of great microporous coloured stains available now. One I use often is "Solignum". Dulux/Sadolin have an even greater range of colours.
With Solignum, you just rub down, then put on 2 coats to finish. No primers, undercoats etc. Not even any knotting needed.
https://www.promain.co.uk/manufacturers/solignum/architectural-water-based-opaque.html