Update - It seems the Declaration Form is coming. Expect it to be announced next week probably but will be enforced hopefully from the 8th March.
See https://assets.publishing.service.go...pring_2021.pdf Page 33 Point 94

"In England, travel abroad for holidays will still not be permitted and, from 8 March,outbound travellers will be legally obliged to provide their reason for travel on the Declaration to Travel form."