We have measured a time delay of 26 ^ { +4 } _ { -5 } days and a magnification ratio of 1.52 \pm 0.05 in the strong radio gravitational lens PKS 1830 - 211 .
The observations were made over the 18 month period from 1997 January to 1998 July with the Australia Telescope Compact Array at 8.6 GHz , and have shown that the source started a large flux density outburst around 1997 June .