I'll have all day tomorrow to see some major sites in London. Given that it will be Sunday, and I am staying in Regents Park, can anyone offer a plan? Should I take tube or bus? I'd like to stop by Harrods, see Trafalgar Square and major sites in that area, Buckingham, Big Ben, and TOL. I know I can't tour all of it one day, but I'd love to see major sites. Just looking for the most efficient route.
Oh-any food suggestions are most appreciated-especially pubs.
Thanks!

I would start with Tower of London and be there before it open so you get through as much as possible before the worst of the crows get there. Assume you will have to allow 3 hours anyway.

If you want to see Harrods I would head there next and grab a quick bite somewhere in the food halls (since it closes by 6 pm).

Many of your other sights are walk throughs and you can do them at your leisure and don;t have to worry about when things close. but do be aware of the time at which it gets dark.

I would try for Westminster Abby in the afternoon but I don;t know what the hours are - you would have to check.

And this would make a very full day.

>>I would try for Westminster Abby in the afternoon but I don;t know what the hours are - you would have to check.<<

No tours of the Abbey on Sundays

The most efficient route would be: Go to the Tower at very first opening, then tube to Embankment station and walk around Trafalgar Square, then walk down Whitehall to see the Abbey/Big Ben/Parliament from outside, then up Birdcage Walk to see the Palace - then across Green Park to the tube station and jump on the tube to Harrods. Since everything besides the Tower is a 'walk-by' You should easily be able to get to Harrods by 4PM-ish.

If you have never been to London before and only had one day, I would highly recommend the on/off bus to see all the sights in the city.I know that quite a few flight attendant friends of mine do that when they are trying to jam as much as possible in one day.
Have fun-I am working a 4 day trip to London tomorrow.

It might be too late for the OP, but Harrods opening hours on a Sunday are 12 noon till 6pm. The store does open at 11:30am but the tills don't open till 12.