Merge pull request #587 from SpiNNakerManchester/fix_routing_again #1897

Job	Run time
call / tests (windows-latest, 3.12, tests)	2m 5s
call / validate (ubuntu-latest, 3.12, validate)	2m 27s
call / tests (windows-2019, 3.9, tests)	1m 46s
call / checks (ubuntu-latest, 3.13)	1m 43s
call / tests (macos-latest, 3.13, tests)	51s
call / checks (ubuntu-24.04, 3.11)	1m 44s
call / tests (macos-13, 3.9, tests)	2m 21s
call / checks (ubuntu-latest, 3.10)	2m 5s
call / checks (ubuntu-22.04, 3.9)	1m 58s
call / checks (ubuntu-20.04, 3.8)	1m 59s
	18m 59s

Provide feedback