Wow - lots of interest. Thank you all. Especially for making me revisit documents and assumptions.
To answer questions:
1: Jean died in Auckland, 15 Jun 1970. Her will, which I have, leaves everything to "my son EDWARD JAMES JONES". It was made in 1962, she signs Jean Burns.
2: The son is referred to in the death notice: "beloved father of Edward". We always knew the son as Jimmy. Games with names! He was living with his mother until the late 50s. I don't know what happened between her son and second husband, but in any case she was with her second husband for a very short time.
3: Jones' age in 1935 was ~51, but she was only 27 so I'm not convinced the son must have been from a previous relationship. Perhaps his appearance forced them to marry or pretend to at least.
4: Her son is recorded as 35 years old on her death registration, hence the estimated birth date of 1935. I'll attach the file.
5: It also records two marriages. Her son must have supplied the information but would have no reason to doubt she was married.
6: She is referred to as proprietress of the meat company in Wises directories from 1946 to 1956. By 1959 the building had been taken over by the Ministry of Works for government offices (it's just across the road from both Govt Buildings and Parliament).
7: Thanks for the mention of the ownership records - I had enquired about them.
It certainly begins to seem that the most logical explanation is that she never formally married Jones, but they had a good go at pretending,
Thanks again everyone.
Slainte
Gordon