Probably an easy one but wiki and professor Google leaves me none the wiser - what are the small, backwards L shaped attachments on the left wings of these WWII aircraft? Seen here on a Hurricane, the left wing on the outer blue circle of the RAF roundel and here on a Spitfire, in roughly the same place.
Pitot tube air speed sensor?
Yep, those are pitot tubes
Ah! Thanks, naita, learn something new everyday.
Pitot tubes malfunctioning/freezing/etc can cause crashes, like this Air France plane near Brazil: Final verdict on Air France 447: sensors left pilots helpless | The Independent | The Independent
longer list from wikipedia:
1 December 1974—Northwest Airlines Flight 6231, a Boeing 727, crashed northwest of John F. Kennedy International Airport during climb en route to Buffalo Niagara International Airport because of blockage of the pitot tubes by atmospheric icing.
6 February 1996—Birgenair Flight 301 crashed into the sea shortly after takeoff due to incorrect readings from the airspeed indicator. The suspected cause is a blocked pitot tube (this was never confirmed, as the airplane wreck was not recovered).[7]
2 October 1996—AeroPeru Flight 603 crashed because of blockage of the static ports. The static ports on the left side of the aircraft had been taped over while the aircraft was being waxed and cleaned. After the job was done, the tape was not removed.[8]
February 23, 2008—B-2 bomber crash in Guam caused by moisture on sensors.[9]
1 June 2009—The French air safety authority BEA said that pitot tube icing was a contributing factor in the crash of Air France Flight 447.[10]
Just for those who haven’t checked out the photos in the OP, those are some really nice high-resolution photos of airplanes. 
Indeed. Two of my favourite airplanes, depicted in stunning photographs!
Since I’m too late to provide the answer to the OP, I’ll share a sign that popped up in front of airport urinals back when I was a teenager:
NOTAM
Pilots with short pitot tubes
or low manifold pressure,
Please taxi close!
It shouldn’t be a NOTAM. It should be in the regs!
On an aircraft, what do they actually do in practice?
They sense the dynamic pressure of the air, that is the pressure of the air due to the forward movement of the aircraft, and this pressure is used to move a needle on a cockpit gauge that is calibrated to show the aircraft’s actual speed through the air (true air speed) at sea level. At higher altitudes the air speed indicator under reads but it still displays a valid speed for aerodynamic properties of the wings, such as showing when you will stall.
Ah!
Thank you Richard Pearse and Johnny L.A.
I must say they sound like they would come in very handy when flying 
Is it pronounced pee-tot or is there a silent letter in there or what?
As a kid, I enjoyed building scale models. The pitot tube was usually one of the harder part to get right during assembly. It is tiny and there isn’t an easy way to clamp it while the glue set and if/when it sets crooked, the whole model looks wrong. Antenna masts like behind the canopy in the Spitfire shot were similarly difficult.
Amazingly, I swear I remember (from like 25 years ago) the little D-shaped bracket behind the wing in the Hurricane pic and wondering what it was. Looking at it now, it looks like it may be a step or stirrup for the pilot to enter the aircraft.
It’s “pee-toe”, being French in origin the last letter is silent.
It’s not uncommon to hear pit-ot or pee-tote.
Glad there’s some appreciators of fine RAF machinery among the Dope. Is there any reason they put them on the left wing in particular?
I love WWII era aircraft, beauty and form.
The CAF flies around here often on the Fourth of July
Was out at my Dad’s house a few yrs ago, kinda in the countryside 45m/72km appx from Houston. Several small airfields around. Hear this powerful low rumble, grab binoculars, fully restored Zero flying around the house.
Lottery Fantasy,
ME 262 with modern engines
Capt
Tradition.
The Pitot tube was on the port wings of the Hawker Typhoon, the Fairey Firefly, the Gloster Gladiator and Meteor, the Republic Thunderbolt, the Lockheed Lightning, The Curtiss Warhawks, (and related birds), Bell Aircobra, etc.
It was mounted on the fuselage of a number of bombers, but on fighters where prop wash could affect the instrument, it was placed on the outboard wing. I have never heard of a specific reason to place on the port wing, but would guess that having it consistently on one side meant that there were fewer incidences of people damaging it because they did not expect to find it somewhere else.
FWIW, a jet normally has pitot tubes on both sides of the nose (the captain and the FO have separate systems for redundancy). A fighter has only 1, also on the nose. There’s no need to get out of propwash, and no need for the lines to be any longer than they have to to get into “clean air”.
I have no idea how many vintage A/C have the pitot tube on the port side but there is an advantage to earlier high wing planes. It gives the PIC a good view of icing conditions and it’s on the side of the cockpit that always has primary instruments on it. Might be an engineering force of habit.