Death
There are a few possibilities

1. 20 January 1743 more likely his father but he would have been only 32 years old
2.7 September 1744 age 33 years
3. 29 May 1772 age 61 years

If this John is the won who married before 1741, no. 3 above is the only option.
There are two John Savill who married around that time one Married Mary, the other Ann. There is not sufficient information to determine either family although both couples had children from 1741.

Below are entries in Radwinter parish baptisms that may relate to John

10-May-1741 Susan Savill John & Mary
27-Apr-1743 Henry Savill John & Mary
6-Jan-1745 Thomas Savill John & Mary
12-May-1747 George Savill John & Mary
26-Nov-1749 Robert Savill John & Mary
3-Mar-1751 Samuel Savill John & Mary
and
28-Nov-1741 Richard Savill John & Ann
7-Oct-1744 James Savill John & Ann
5-Jan-1746 Samuel Savill & John & Ann
10-Apr-1748 John Savill John & Ann
13-Jan-1751 Elizabeth Savill John & Ann