Sorry to hear mate..
Insurance should cover you from the date the policy was agreed on. Just make sure you pay it asap.
Has it been reported to police? Insurance will need a police report, to verify when the accident happened, and various details.
It may not be worth claiming though, depending on damage and your excess amounts.
Ring JC and ask, they were very helpful with me everytime I rang with a question.
Hope the rest of your Xmas was merry!!