Dianne Thompson, the group chief executive of the National Lottery operator Camelot, is 61 years old and small in stature, but she doesn't lose many battles.
A decade ago, Thompson saw off Sir Richard Branson when his People's Lottery bid against Camelot for the lottery licence. Now she is taking on the media owner Richard Desmond, whose Health Lottery, she claims, threatens the long-term viability of the National Lottery. "It is my fortune in life to be haunted by Richards," she jokes.
Camelot claims the Health Lottery is unlawful and the Gambling Commission should revoke or suspend its licences. Last week it applied for a judicial review of the commission's refusal to do so.
The Health Lottery consists of 51 society lotteries with the same three directors. Society lotteries cannot be set up primarily for commercial purposes; Camelot contends that the Health Lottery flaunts this principle.
It also claims the Health Lottery is, in effect, a nationwide operation, which contravenes the 1993 act that conferred monopoly status on the National Lottery. It says Desmond's operation costs it £1.5m a week.
The Health Lottery denies it has broken the law and claims it is growing the market. The Gambling Commission, meanwhile, says Camelot has "no arguable ground and no realistic prospect of success".
Thompson, a butcher's daughter from Yorkshire, estimates Camelot's legal costs will be "significant" but "less than seven figures".
She may have to take the witness stand for the first time ever. "I'm not relishing it, but it comes with the territory," she says. "I feel strongly that someone has to do this to stop a precedent being set."
If the Health Lottery is left unchecked, she says, other firms could form similar ventures and "in three or four years it will be the end of a relatively thriving National Lottery".
Camelot spent three years and £20m producing an 18,500-page bid document when the licence came up for renewal in 2009. "If this goes ahead unchallenged and we get other players coming into the market, we can envisage a situation where there won't be anything worth bidding for next time," says Thompson. "Everyone will go through the back door."
Five years ago Play Monday spent £8m advertising itself as a national game before quickly collapsing. Why didn't Camelot take legal action then? "It was fairly obvious from day one that it was going to fail," says Thompson. "£8m sounds a lot, but it runs out quickly. Desmond is claiming that he spent £35m. This is a very much more serious threat."
Thompson praises Desmond's business skills and philanthropy. "I might not totally approve of all the pornography stuff he does - it's not my bag - but you can't help but admire the guy," she says.
"We think what he is doing is illegal, but if it turns out that it is legal, then he has exploited a very clever loophole in the law."
She is less complimentary about politicians. The Department for Culture, Media and Sport wants to assess the Health Lottery's impact on National Lottery ticket sales before taking any action.
"The DCMS owns the National Lottery - it should be the one fighting for it," says Thompson. "It was hoping, I think it's fair to say, that the Health Lottery would fail. But of course it didn't."
She has spoken to the lottery minister, John Penrose, and the culture secretary, Jeremy Hunt. Two months ago she wrote to the Prime Minister, David Cameron. She has yet to receive a reply.
Even if Camelot wins, it could be a Pyrrhic victory that merely forces the Health Lottery to restructure. But Thompson says it has no choice but to fight. "As long as we are custodians of the National Lottery, we must protect it," she says.
The judicial review is a rare cloud in the Camelot sky. This month, the National Lottery Commission extended its licence from 2019 to 2023. By then it will have run the game for 30 years.
It plans to set up another 8,000 ticket outlets in mainly rural areas by 2023, which it claims will generate another £1.2bn for good causes.
Camelot keeps 5p from the sale of every £1 ticket - 4.5p in operating costs and half a penny in profit. Fifty pence goes to the prize fund, 28p to good causes, 12p to government and 5p to retailers.
The company, which employs about 850 staff and was bought by a Canadian pensions company in 2010, has increased ticket sales by 20 per cent since 2002. It now generates £30m for good causes every seven days. "A Children in Need every week," says Thompson, who was described by the Daily Mail last year as "hard as nails and very, very driven".
She plans to step down in 2015 and would consider running a charity. But for now, the courtroom beckons.
2000: Chief executive, Camelot
1997: Commercial operations director, Camelot
1994: UK marketing director, Signet Group
1992: Director of marketing, Woolworths
1988: Managing director, Sandvik Saws and Tools
1986: Marketing director, Sterling Roncraft
1979: Lecturer, Manchester Polytechnic