According to claim documents, Mrs Offord was a part-time relief postperson in February 2016 when she was asked to cover for a colleague.

The colleague had noted the presence of the dog, on a route in the Lowshoe Lane area of the town, her lawyers claim.

The dog had been "aggressive," biting and pulling post through the letterbox, but this was not recorded on the route log, the document says.

Her lawyers state: "She was delivering a parcel. She rang the doorbell. The occupier did not answer the door.

"The claimant, as she had been trained to, filled out a form P739 - 'Something for you.'

"She pushed the form through the letterbox. As she did so, the dog bit her, causing serious injury to her fingers."

Mrs Offord's legal team say she had been told never to leave an item hanging out of a letterbox, due to the risk of theft.

But she had not been given a posting peg, a plastic device used for posting mail without postpeople having to put their fingers through the letterbox.

The presence of the dog was also not noted on the "walk log" and so she had no idea of the risk she was taking, it is claimed.

The case was in court for a short preliminary hearing ahead of a full trial of the claim at a later date.

Mr Rodgers told Judge Caroline Wilkinson that the owner of the dog - the breed of which is not known - was convicted of a Dangerous Dogs Act offence.

According to a local newspaper report the dog's owner pleaded guilty to being the owner of a dog dangerously out of control causing injury in May 2016 at Barkingside Magistrates Court.

The owner was reportedly ordered to pay fines, compensation and costs totalling £8,793 from which Ms Offord received a compensation order for £2,764.

Additionally the dog was hit with a "contingent" (or suspended) destruction order, meaning that any further offences would result in the dog being put down.

However, Mrs Offord had decided to sue Royal Mail and not the dog owner because of alleged "wider issues" within the sorting office, Mr Rodgers said.

The "walk log" for that particular route had not been updated since 2011 and did not record the presence of the dog, he added.

He also claimed managers at the Romford sorting office had failed to take "reasonable care for the safety of their post persons."

As well as the cosmetic effect of losing her fingers, Mrs Offord has been left suffering with "cold intolerance," which may impact on her employment with Royal Mail, he continued.

The court heard Royal Mail is defending the case, denying liability for Mrs Offord's injuries and contesting the size of her claim.

Lisa Fountain, from Mrs Offord's solicitors Slater and Gordon Lawyers, said: "My client had been in the job for less than six months at the time of this attack, which has caused serious and permanent disfigurement.

"Several thousand people are attacked by dogs each year including many postal workers so this should have been a known risk for Royal Mail."

According to Royal Mail, 47 postmen and women are attacked by dogs in the UK every week.

A Royal Mail spokesperson said: "We cannot comment on this individual case as it is ongoing. However, we welcomed the prosecution and conviction against the person in charge of the dog at the time of the attack.

"Royal Mail treats all dog attacks on our postmen and women very seriously, and our first priority as an employer is to ensure the welfare and safety of our people who provide a valuable service to our customers.

"It is very distressing when one of our people is attacked by a dog while carrying out their job. We continue to appeal to dog owners and their families to take steps in order to reduce the numbers of attacks, particularly through letterboxes, at the door and in the garden."