Pocket knife /Swiss Army knife       
Steed opens the boxes with the stamp collections in The Mauritius Penny with a
Swiss Army Knife and used it again to cut free Olga in The Correct Way to Kill. He
used another pocket knife to break in through the window in Invasion of the
Earthmen and asked Venus if she could reach for his pocket knife in Man in the
Steed is writing postcards to his partners or friends when he on holidays or on  
missions, but sometimes he forgets to put a stamp on it. Mrs Gale reminds him of  
the stamps in The Undertakers and he did sent a card to Tara and another one to  
Mother with a picture of Bacchus on it in Stay Tuned.
Steed shaved in Too Many Christmas Trees; Steed is using a Philips Philishave  
battery shaver with two rotary heads from 1967; the commercial slogan was: "For  
the man on the moon" - quite Bizarre!
He shaved In A Chorus of Frogs, The Golden Eggs, Too Many Christmas Trees,  
Dead Man's Treasure and he's using a razor in Invasion of the Earthmen but only  
to cut a bag with it.
A running gag in the third season of The Avengers was Steed's statement:

"I ​​do not smoke".

While Steed did not smoke anymore, or at least a cigar on rare occasions, Patrick  
Macnee did - up to 80 cigarettes daily. There are many set photos on DVD with  
Macnee smoking from season 2 to 6.
Several people were Patrick Macnee's doubles or stand-ins, amongst  them: Mike  
Stevens, Cliff Diggins, Ray Austin, Joe Dunne, Rocky Taylor, Paul Weston, Brian  
Chuter and Eric Woofe.
The name of John Steed's tailor is Lovell (The Wringer).
Tintin et Milou
Steed is reading four different Hergè comics during The Avengers.:

The secret of the Unicorn - The Outside-In Man
Le Lotus bleu - Look - (Stop Me If You've Heard This One) But There Were These  
Two Fellers...
Tintin au Pays de l'or noir (French version) - The Golden Fleece
Tintin in Tibet - Man With Two Shadows

Steed did not read a Tintin et Milou comic in the Emma Peel era nor in The New  
Trivia I - NHomeTrivia U to Z
John Steed Trivia from O - T