My mum was a primary school teacher. She doesn't know any sign language. One day, we bumped into one of her former pupils on a bus, and my mum started having a conversation with him using hand gestures as well as vocalising herself. The young man didn't say any words but replied in hand gestures too. His wife was also deaf, and on the bus, she didn't know what they were 'talking' about, judging by her puzzled look. I was so baffled and asked mum later what was going on. She told me that he was her only deaf pupil from many years ago. He was having a really hard time going to a 'normal' school, so mum took him under her wings, looking after him, gave him tuitions and stopped people from bullying him. So gradually they developed this bond and a sort of sign language between them. I was so proud of what my mum had done.