I've spoken to my mum, the children are at the fair this afternoon, but she will go round for their tea time and just hang around pretending she hasn't seen them for a while and see how things look. Her feeling is we have to see what ds says, whether the nanny had said she was going out for five minutes. If she did then we'll call her in over the weekend, hear her story and if we think she's lying we'll have to ask her to leave. If she admits she was intending to go home, then yes, we'll have to sack her.
I'll try and answer a couple of points...
Ds can open the door using the Yale lock, and he does have a tendency to follow someone out if they're going out the front door so it's possible she double locked it because she didnt' want him wandering in the street.
Outraged You're right about the cultural differences thing, she's not English. I suggested that might have been the situation at the time of the shop incident but several people from the same country as her came on and said they wouldn't have dreamt of leaving a child in a shop alone so I discounted that.
She does have extra insurance to cover our children in her car, she also has up to date first aid (she only updated the course recently). She doesn't have professional insurance, but she's not formally trained (been working in childcare for 12 years).
She does work for another family 2 days a week as well. They absolutely rave about her. If it turns out she was intending to leave my children alone, and I have to sack her, do I tell the other family? We were supposed to be doing a nanny share 1 day a week from Sept until Christmas. They'll want to know why we're not going ahead.
Dh is ok with the nanny, hasn't commented on her much. Grumbles occasionally that she doesn't tidy up much, but that's it and frankly it's the pot calling the kettle black
The handbag is so odd. I would never leave someone else's children alone, but if I did I would literally jump in the car, no handbag, no child. Just car keys and house keys and go.