Hi PD's..... in a recent snap..... ...Eddy posted a view looking onto the bridge of PS Waverley.....but three of the four ventilators were facing AFT & would apparently not catch any breeze to supply the lower deck/engine space/boiler space with natural air convection

I rest my case  ...or does this confirm that AIR blows backwards in UK....

The wind passing around the ventilators facing AFT is creating a low pressure zone in the vent throat this depressurized zone is filled with air from the lower decks which supplies forced air convection.
Regards,
Gerald
PS This was written at 7:20AM BC(before coffee.)

No, the air only blows backwards if you are standing upside down....er...a bit like you chaps 

Well good morning PD's & Gerald....please enjoy your .....& we appreciate your comment/question...

....we have a twofold question here

1) 'Ventilators' [to move air] ...do admit air & so attempt to maintain a higher pressure so as to displace...

2) 'Ventilators' [to move air]...via the expulsion of air  via venturi effect [similar looking to ventilators]....but a bit different....looking 

I fully acknowledge that a backwards facing [to the wind] ventilator will cause a negative pressure draw....so we should get some of the PD members  .....on board the said vessel to offer comment here