RAT was installed in a small number of practices in Northern Ireland in 1996 and was an instant success. Over the next twelve months, more GP practices heard about the software and began using RAT.  In 1997, I entered a competition and won the 'John Perry' Prize, Primary Health Care Specialist Group of the British Computer Society (PHCSG-BCS) in September 1997 at the annual meeting at Cambridge University. I was presented with a replica of a pewter bowl found on the Mary Rose, the flagship in King Henry VIII's fleet. Quite a fitting prize I thought considering the subject matter.

The Mary Rose ship sank in the Solent in 1545 but this left a wonderful treasure trove of Mary Rose artefacts providing an insight into life on a Tudor warship. On board Mary Rose was a barber-surgeon, with his own cabin. He cut hair, he pulled teeth and he performed simple operations such as amputations and setting broken bones. In Tudor times medicine was dominated by the theory of the four humours. People believed that the body was made up of four humours or liquids. They were phlegm, blood, yellow bile and black bile. If a person had too much of one humour they fell ill. For instance if a person had a fever he must have too much blood. The treatment was to cut the patient and let him bleed.The two-handled bowl came from the Barber-surgeon's cabin. The bowl, either a bleeding bowl or more likely a porringer, was stamped with the letters 'WE' possibly the initials of the Barber-surgeon.

RAT received much interest from doctors at the PHCSG-BCS meeting who requested copies of the software. In those days the 'world wide web' was in its infancy. The RAT installation files were stored on four floppy discs, remember those? I posted a number of these to practices across the UK in 1997.

In the summer of 1998, I entered a paper for the WONCA conference in Dublin, Ireland. INR monitoring in primary care was a new concept at that time and RAT was well received. Over the next five years RAT use across the UK expanded greatly. RAT has never been commercially marketed. I have always presented RAT in a clinical setting and preferred to have doctors personally recommend the software to their colleagues and it is through this means that RAT has had great success. Over 600 practices are currently registered in the UK and beyond. Its success through word of mouth has ensured that RAT continues to be a leader in primary care INR monitoring in the UK.

RAT has many, many person years of experience over the past fifteen years. The core decision making algorithm in RAT has not been changed since the first 12 months of development and only a few minor modifications to the dosing regimen over the years. The dosing algorithm is based on a paper in the British Medical Journal 1989;299:1209-10. In fact, the past five years have seen no changes to the regimen. There have been various modifications to the user interface and administration parts of the software every 12 months but nothing too radical. RAT has also been used in various audits over the years, some I probably don't even know about!

The Rat user interface was designed to be intuitive from the start and it is a testament to the design that I have had no users requesting major review of the RAT software. The design was in the shape of 2 Lloyd-George medical folders similar to traditional primary care record keeping. The straight forward design also means that RAT does not need any hands-on training. Good software should not require any intensive training, think of any PC software you currently use. Of course there is some functionality that isn't immediately obvious to the user but it's not crucial to the core functioning of the software.

I decided after the first few years to set up a public online support forum. I deliberately wanted to let all existing users and potential users view any current RAT issues and queries. INR monitoring is such an important area that I felt users should have easy access to current issues. I believe this policy of being transparent and open has been important to all users of RAT. Not all software developers will do this. You can browse the forum to get an idea of what users are currently saying about RAT.

Although most RAT users are in the UK, RAT is truly global. It is used in New Zealand, a few practices in Australia, one in the USA and is also installed in a practice in the Falklands Islands.

If you want to evaluate RAT, download the full software and use it free of charge for four months. After that time I request a registration fee of £399.00. This includes 12 months email support. Thereafter annual licence and email support is £169 per annum.