Write SQL query to solve given problem: Which Apollo Ltd customer's order number has the most expensive unit price, indicating the order date?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T1.OrderNumber, T1.OrderDate FROM `Sales Orders` AS T1 INNER JOIN Customers AS T2 ON T2.CustomerID = T1._CustomerID WHERE T2.`Customer Names` = 'Apollo Ltd' ORDER BY T1.`Unit Price` DESC LIMIT 1