According to an the National Delivery Plan 2020-2025 of Highways England,  the expected start date for work for the already delayed A303 Stonehenge Tunnel project has been pushed into late 2022.

In addition to the COVID-19 delays, Stonehenge Tunnel construction has also been already delayed by new archeological discoveries nearby. 

For details, you may want to read the National Delivery Plan 2020-2025 document at the Highways England site.

https://highwaysengland.co.uk/media/vh0byhfl/5-year-delivery-plan-2020-2025-final.pdf