What is the fine-grained topic of the following text: More than 100 competitors took to two-wheels for the gruelling Mersey Roads 24 Hour Time Trial around Merseyside but Christina was in imperious and unstoppable as she left her rivals choking on her slipstream with a dominant ride as she set a brand new British record. Only return the topic.
Christina's record-breaking performance in Mersey Roads 24 Hour Time Trial