Most legislation begins with the Government, and has teams of civil servants and lawyers working on it. For an individual member to introduce a bill and take it through parliament is no small task.
My only experience of this was a bill about hate crime, and it ran to just over two sides of A4.
Short and simple, it took a mechanism which already existed for racist crimes and applied it to other crimes of prejudice.
The Government was supportive, and apart from a few anti-equality voices from the fringe there was little opposition.
Even so, it was a fair amount of work.
Now I've taken on something much more substantial.
Last year I agreed to act in a sort of "understudy" role for Margo MacDonald, who was proposing a bill on assisted suicide.
It was her second attempt to address this complex subject, and the new bill involves additional levels of detail to answer objections raised last time round.
It's also a subject which raises really big questions: about life and death; about distressing circumstances we all hope we'll never face (though a great many of us will) and about the values by which we live.
Far more than a small technical change in the law, this is a challenging and emotionally charged debate.
Margo was aware that her own health was unpredictable. She had lived with a diagnosis of Parkinson's Disease for more than 15 years, and an increasing burden of symptoms and a cocktail of medication.
It was impressive enough that she managed to continue as a formidable MSP, but also to act as the standard-bearer for assisted suicide was pretty well heroic.
But though she remained an impressive figure in Parliament on her good days, she knew that not every day was a good day, and she asked me to stand ready to step in for her if she wasn't able to be there on a critical day for the Bill.
Now that Margo is no longer with us, it falls to me to lead on this Bill.
We know that there's a majority of public support for a change in the law to allow people - in certain carefully defined circumstances - to take control of the end of their lives in an atmosphere of love and compassion.
In recent weeks the issue has hit the headlines with comments from celebrities such as Richard and Judy, and Patrick Stewart.
But there's just one name which will always be associated with this issue for me - Margo.
I hope I have what it takes to give her Bill the chance that her memory deserves.