What happened to Old London Bridge? [video]

A small interesting detail: the 1630 painting of Old London Bridge shown in the video (at 2:07) can also be seen here on Flickr.

https://www.flickr.com/photos/vikingman/35359854511

At the start of the bridge you can some spikes and blobs displayed. What are they?

> "At the southern end of London Bridge, close to the riverbank, stands Southwark Gate. De Jongh [Dutch artist Claude de Jongh] has depicted the skyline bristling with the severed heads of traitors, displayed on spikes as a warning to citizens and visitors. The first unfortunate person whose head was displayed at Southwark Gate was the Scottish knight William Wallace, executed in 1305. Over the centuries, the heads of many more famous traitors were so displayed, including the rebel Jack Cade, Henry VIII’s former Lord Chancellor Thomas More, Thomas Cromwell and Guy Fawkes.

> Maintaining this macabre spectacle was the job of the ‘Keeper of the Heads’. He was responsible for first preserving the heads by parboiling and coating them in tar, and then impaling them for display. After two to three weeks, he removed the weathered skulls from view and discarded them in the Thames.

Source: https://www.english-heritage.org.uk/visit/places/kenwood/his...