best London tour in a day

You can browse their website to see if any of the walks offered by London Walks interests you and fits your tight schedule.

https://www.walks.com/

The sites in London are so spread out that I'd be surprised of a tour that covered everything. The Tower of London itself could fill your day. The above poster recommending London Walks is a good idea.

Walk around by yourselves.

You’ll arrive from Paris at St Pancras station.

Follow signage to Kings Cross Station using the modern LCD lighted tunnel walkway and board a Circle line London Underground ( tube ) train to Westminster.

At the interesting looking Westminster station follow signage and exit. You’ll be across the road from Parliament. If you arrive on the hour you’ll hear Big Ben toll.

Wander about Parliament Square. Unless you pre booked a Westminster Abbey ticket the wait will be long.

TakeBirdcage Walk and follow it past St James Park up to the Palace. If the Royal Standard is flying The King is in residence.

From Buckingham Palace and the Queen Victoria Memorial make your way to Green Park by using the paths through Green Park and turn right onto Piccadilly. You’ll walk past the high end hotels ( The Ritz, The Wolsley)….

Keep walking. Window shop. Grab a nosh. Then head off to Trafalgar Square. Turn right and head down Whitehall back to Westminster Station.

Perfect day out in London.

London Walks is a good idea. I would choose 2 sights I wanted to see(to me, Tower of London, Westminster Abbey, British Museum are the most important) and do those on my own.

I just wanted to mention that the Hop on Hop off bus in London is not a good option for someone with limited time. You would think it was a time saver and convenience, but it is in fact the opposite. You spend your time viewing London Traffic Jams and taking routes that are far from efficient.