Best route to long marston old raf air field from m40, 
driving dd please
You’ll have to go into Stratford so I’d have thought junction 15 , a46, A439, a3400, b4362 past Clifford Chambers.
Can’t think of any bridges that way but best check before hand.
A46 then A3400 a P&R island. Follow straight into Stratford and you’ll go round a one way system/large island. Take the road that goes over the river (narrowish bridge) and turn right after bridge, over one island and r8ght at second island (Morrison’s) and follow.
You don’t have to go into Stratford at all
Come off the M40 J15 head down the A429 to Ettington, turn right onto A422, head up there to the little bypass, picking up the A3400 then turn right onto the B4632, follow that and the airfield comes up on the right!
toonsy:
A46 then A3400 a P&R island. Follow straight into Stratford and you’ll go round a one way system/large island. Take the road that goes over the river (narrowish bridge) and turn right after bridge, over one island and r8ght at second island (Morrison’s) and follow.
Just letting you know it is sign posted 11’ 3" bridge at morrisons island, but you reach the airfield before the bridge, and turning into the airfield looks like you are entering a housing estate which you are but it is the only way in.