Lennox's parents have maintained a vigil at his bedside

Lennox Nicholson, who is five months old and from Teesside, developed jaundice and chronic liver problems soon after his birth.

Parents Simon Nicholson, 21, and Amy Robinson, 20, launched a donor appeal last week.

The operation to transplant half an adult liver began at Leeds St James University Hospital on Tuesday.

Lennox's grandmother June Nicholson was told the news by her son.

She said: "We just wanted to open the door and shout out and tell everybody.

We are very nervous but also very happy June Nicholson

"We were warned there's always a chance it can get to the table and not be suitable, but we have heard no more so we are hoping the operation is going ahead.

"Hopefully this potential donor has turned out to be suitable.

"We are very nervous but also very happy."

Lennox was born on 21 June weighing 7lb 1oz and appeared to have no problems.

A later operation found his bile ducts were completely blocked.

Mrs Nicholson said her grandson had deteriorated in recent days.

"It was dreadful how much he had gone downhill, he was getting so weak and I was really concerned about him."

A Leeds Hospitals NHS Trust spokesman said: "The operation involves a section of adult liver and is not expected to be finished until later this evening."