By Laura McGuire London Cocktail Club owner Nightcap had a “record” Christmas despite ongoing rail disruption and cost of living pressures. In a trading update published today, the late-night bar chain operator said revenue reached £9.2m in December, the highest level for the month since the group’s listing in London three years ago. Shares soared 19 per cent this morning as investors were dazzled by its performance. The business, owned by former Dragon’s Den star Sarah Willingham, also said unaudited group revenue shot up 39 per cent to £18m in the 13 weeks to December. Rail strikes have been…