Assuming you mean in London, there are a number of good pubs in South Bank or Southwark. One of my favorites, just for pure history is The George, a pub dating back to the 1600's, decent cask ales, OK food. Nearby is the Old Kings Head, another ancient pub, more local than tourist, one of the first London pubs I visited, so somewhat sentimental. Near Borough Market is the Market Porter, just spending time in the market, maybe for lunch, then a stop here is a good time spent; the style of beer "Porter" comes from beer served originally in the area that was a mix or midpoint between a Stout and an Ale.
You can also seek out some pubs near the river; the Anchor Bankside comes to mind, nice outside area overlooking the river, bit touristy, but still solid. Less historic would be the Old Thameside Inn, a part of the Nicholson chain, decent but standard menu, but good views of the river and skyline.
Lots of other places just to bump into and have a pint, but the above is a good start.