The Government guidance on this point is not particularly clear. At the time of writing, the Government advice is that, save for key workers, people should only travel to and from work where "absolutely necessary".
It is not clear what "absolutely necessary" means, but it appears that the advice is that people should only go to work in circumstances where they cannot do their work from home. Currently, it seems therefore that employers can require their employees to come to work, but only if they are unable to work from home. Employers should ensure that employees can adhere to social distancing guidelines as much as possible to reduce the risk of the spread of the virus. This can include measures such as allowing staff to travel at quieter times, paying for parking so staff can drive to work and ensuring social distancing of at least two metres (6ft). In some industries this poses particular problems and the government may provide further guidance in the coming days, with the possibility of a total shutdown on all work, save for key workers, looming.