By 1903-4 Grand Avenue was complete, with the corners neatly turned ready for Firs, Birchwood, Fortismere and Leaside Avenues to be built later, although no house had been started in any of these roads. Collins had outlined his estate by building Collingwood and Grand Avenues and had reserved the whole of the valuable Fortis Green and Fortis Green Road frontages for flats and shops. Some of the flats were not to be built for more than twenty years.
Next Collins began to close in from both sides towards Fortismere House, where he was living with his family. The original Firs House was still occupied by Thomas Wilson until at least 1901, but by 1906-7 Firs Avenue, the shops and flats of Firs Parade, and the first few houses of Birchwood Avenue had all been built. In the same period, Leaside Avenue, together with Leaside and Midhurst Mansions, had been completed. Collins was finally approaching Fortismere House itself.
Fortismere must have been an ideal place to bring up a growing family and he put his bailiff, Thomas Batten, in Fortismere Cottage, the building which had been occupied by the coachman Narroway in 1881. Collins was now living comfortably in a large house with his estate rising around him.
Fortismere was not listed in the 1901 Street Directory, so we do not know how he used the second Fortismere house. He may have let it, or used it as offices, workshops and stores, only demolishing both houses at the last moment, in perhaps 1909.
It is worth breaking off here to discuss the Collins family as it shows how a Victorian/Edwardian father planned for his business to be continued.