Why is Alfie suddenly barking at people and growling on walks

[NotanotherAlfie!]

In the last few weeks Alfie has suddenly changed his behaviour whilst on his lead.  If we meet anyone with or without a dog he stands there barking and growling at them.  It is beginning to get embarrassing and I know that a lot of people will automatically assume he is a nasty dog.  This morning an old lady was walking towards us and she started to talk really gently to him he started growling at her and barking and pulling on the lead (wagging his tail at the same time!)  I have started talking gently to him when people approach saying "good boy" under my breath so only he can hear me.  He seems to respond to this very well and will walk past people like he used to.  Trouble is like this morning the lady kind of came out of no-where and I did not get the chance to talk to him  Why is he suddenly doing this, do you think he could turn into a nasty dog (he is 2 on Sunday).  Anyone got any ideas or advice, I can tell non dog owners are wary of him and he really is a big softie.  But I am concerned now that if he was not on a lead would he attack.  Recently he went mad at the window cleaner who comes regularly, he is a dog owner so was not put off, Alfie ran out the front door barking but ended up laying on the floor on his back for a tummy rub.  I am confused as to what he is thinking.

[MaggieR]

Not sure why it happens but same thing happened about the same age with Maggie... she took it upon herself to tell anyone off she felt was in the wrong place at the wrong time or people she didn't know, for the most part its isolated to the park where she has a pretty clear expectation of what should/shouldn't be there.  When we're out other places she's fine...
For the most part does it off lead, but that might be because she's offlead all the time at the park.  I have to try to spot what will kick her off and distract her while we pass it or it passes us.  Taking a lot of time but getting slightly better.... she wouldn't attack anything and I wouldn't worry that Alfie would either.  When Maggie does it to a dog/person and they look at her or try to go towards her she legs it whimpering 

[NotanotherAlfie!]

Thanks, it's a horrible feeling though when you see the look on another persons face and you know what they are thinking, as in, "what a nasty dog", when really Alfie is a softie. 

[PennyB]

best thing is to try the 'food bar technique' - be proactive and before he gets to the point where he does this you're already feeding him treats (get him to keep looking at you - which is why he gets the treat each time he does) and keep doing so till you go past them.

Wilf gets gobby/grumbly around certain dogs so if I see them in the distance I begin doing something similar.

[Claire_H]

My Honey has started doing exactly the same.  She'll start barking at people for no reason.  She's just turned 2.... maybe it's the terrible two's! First of all I thought it was hats that she didn't like, but it can be anything or anyone, a postman's bike, someone walking across the field we go to, a lady with a shopping bag - she just starts barking for no reason!  I agree it is embarrassing because people look scared and she's such a softie.... it's a real puzzle.