Saturday Day Travelcard
This is ONLY for Saturdays and ONLY for a day trip. You must book by 6PM night before and specify the outward (Manchester to London) train. You can book any time train for this.
While you're in London you can go anywhere anytime on tubes, buses, trains and trams in zones 1-6. This is normally £12 on its own.
Coming back you can get ANY train, you can reserve a seat if you wish but still do not have to get on that time trains.
All trains on this deal are the normal fast direct Virgin trains. Every 20 minutes for most of the day, every half hour in evening.
There are NO railcard discounts for this fare.
This offer's been running for years and is permanent, just not advertised much.