A formal letter of intent was sent to Vickers on 18 February , and its selection as lead yard was publicly announced on 11 March 1963 .
The only concern was whether the large Polaris boats could navigate the shallow Walney Channel .
A formal letter of intent was sent to Vickers on 18 February , and Polaris ' selection as lead yard was publicly announced on 11 March 1963 .
The only concern was whether the large Polaris boats could navigate the shallow Walney Channel .