Joanne Spencer, 47, was given an indeterminate sentence for public protection at Leeds Crown Court and ordered to serve at least three years before being considered for parole.

But a judge told her on Friday she was effectively being given a life sentence and her release "may well be many, many years hence".

The court heard how Spencer, who used to be man but had undergone a sex change, set fire to her flat in West Yorkshire in June after allegedly attacking an elderly woman living nearby.

When police arrived she refused to come out. The court heard Spencer was wearing camouflage clothing and a gas mask.

Officers said she told them she was wearing the gas mask because she wanted to die in the flames rather than from the fumes. She was eventually dragged from the building.

The court also heard about a second incident, in July, when Spencer threatened to kill a taxi driver and racially abused him while brandishing a large hunting knife. The man was left terrified by Spencer and police had to use an electronic stun gun to subdue and arrest her.

On Thursday, Spencer admitted arson being reckless as to whether life was endangered, making threats to kill and possession of an offensive weapon.

On Friday, the Recorder of Leeds, Judge Peter Collier QC, heard she had a string of convictions for violence which had seen her given prison sentences totalling 10 years since 1982.

He said he was taking into account a psychiatric report which said Spencer had a personality disorder and a "significant problem with anger".

The judge said he had no choice but to give her an indeterminate sentence for public protection. He said: "There is a serious risk to the public of serious harm."