leak or no leak?

yesterday we had gales and over 2 inches of rain.
I noticed that the 'cardboard' flue for the gas fire was damp, not dripping wet just a bit damp.  the ceiling around it (say one inch away) was reading 15% on my Micky Mouse damp meter but 2 inches away was reading nil.

could this be water blown down the top of the flue or do I have a problem?

Had the same problem on the Sigma ,when pitched up in Whitby during a weekend of gales and rain, soon dried out with the gas Fire on.
The Sigma a had a roof shaped like an up turned small dingy ,it collected water on the roof,I set the rear air ride or levellers to enable to water to drain off the rear.
Boaby

I had this happen when six inches of snow on the roof started to melt, water discoloured the first 8 inches or so of flue pipe.
It soon dried when the gas fire was used, but the flexible flue pipe is still stained.
I believe there's a flue outlet extension available that raises the outlet, but while this might work for snow, I doubt it would with horizontal rain...
Al.

You don't describe the circumstances, temperature in van, electric heating in use, etc? If the temperature in the van is high and that in the flue cold, you will get condensation (a lot) on the outside of the flue.

the van is parked up unheated, the flue had new rubber seal fitted (precautionary) maybe two years ago, there is a flue extention fitted (fire wouldnt light on even a breezy day without it).

The weather was horrendous with driving heavy rain for 12 hours or more I will lift the drivers side a bit to make sure that water isnt pooling around the flue and see if that helps

I always pop a plastic bag over the cowl when my 'van is not being used in the winter. I did notice the wet rings on the flue pipe a few years ago and started using a bag.  Never have a problem now, just remember to take it off when starting to use the 'van again!

I noticed on my motorhome that the flexi stainless steel chimney flue does not go high enough to sit under the lip in the plastic chimney , water can get between the flue and plastic chimney and wet the cardboard.  I bought a new chimney and had made a top hat section 100mm long from hard nylon , it was a tight push fit into the chimney,  there is a bevel edge this top hat  lip can sit on,  I put a bead of glue where the lip of the top hat sits to form a seal once pushed in it acts like a funnel , the water can drip down the flue and out at the bottom, , the gases from fire can still get out as the walls of the top hat was only 1mm thick. The machine shop measured the chimney and made it to suit. Cost of nylon and machining was 40 quid  new chimney 16 quid. Hope this helps