Significant accounting policies - Property, plant and equipment (Details)	12 Months Ended
	Mar. 31, 2021
Minimum | Machinery
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	3 years
Minimum | Office equipment
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	3 years
Minimum | Computer equipment
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	3 years
Maximum | Machinery
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	5 years
Maximum | Office equipment
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	5 years
Maximum | Computer equipment
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	5 years