You can't always trust a client.
This lesson was learned when I had a client who had consent for seventy or eighty dwellings to be built on the southern side of a village. Unfortunately the then Ministry of Transport had put a village by-pass line right through the site, sterilising the proposed development. Without initial fee and on the footing that I would sell the dwellings if I could get the by-pass moved, I did succeed in persuading the Ministry to drop the idea of a Southern by-pass. Quite a major achievement I thought, but the builder reneged on his promise of sales.