Does having a nut allergy with a restriction on the Class 1 medical preclude someone from securing a pilot job?

Hello Rita, in a nutshell you may be unfit with the CAA until sufficient information is available for the regulator to complete a fitness assessment. More information is available by the CAA https://www.caa.co.uk/media/rb2aq5qm/20231030-v1-0-allergy-flow-chart.pdf I hope that helps. Sorry if it wasn't the answer you were hoping for. All the best!