The law is very clear that employers must make reasonable adjustments for employees and job applicants who meet the Equality Act 2010’s definition of disability, namely having a physical or mental impairment that has a substantial and long-term negative effect on the person’s ability to do normal daily activities. Where a disability is not obvious, it will be necessary for the employee or job applicant to declare their condition, but at that point the onus passes to the employer to meet its legal obligations.
To help employers comply with the law, the Government has issued guidance on the duty to make reasonable adjustments, here: https://www.gov.uk/reasonable-adjustments-for-disabled-workers
In addition, guidance on this subject has been issued by Acas and by the Equality and Human Rights Commission, which has also published a statutory code of practice for employers. Where employers fall short on their obligations, legal remedies exist for employees and job applicants, together with Acas’s early conciliation service, which aims to settle disputes before they reach the employment tribunal.