The present church was built in the Decorated style in 1891 on the site of a previous Georgian church built in 1733 by Revesby Abbey estate owner Joseph Banks, the great grandfather of naturalist Sir Joseph Banks.
'Died on Saturday last, at Mareham Ie Fen, after a severe and lingering illness. Mr James Roberts, aged 74. In 1768 and the following years, this gentleman accompanied Sir Joseph Banks in the first voyage of Captain Cook around the world; and in 1772 he again accompanied Sir Joseph in his voyage to Iceland. In 1795 he retired to Mareham House, where he spent the remainder of his days. Mr R was the last survivor of those who accompanied Captain Cook in his first voyage'. Cinque Ports Herald, Dover, 22 July 1826.
He was buried in the churchyard at St Helens but the sandstone gravestone was eventually brought into the church to avoid further erosion. Above its cambered head is a plaque in his memory.
St Helen is a fine, greenstone, Grade II* listed village church dating from the 13th century.
The tower consists of three stages with an embattled parapet and crocketted pinnacles at each corner. The south aisle dates from the 15th century and also has crocketted pinnacles featuring human heads and gargoyles. The church was partially rebuilt in 1879 and the 19th century south porch leads to a 14th century doorway.
Outside in the churchyard can be found a medieval stone cross dating from the 14th century and restored in 1904, now a scheduled monument.
The nearby Grade II listed Royal Oak pub is well worth a visit. Take a look at the date stone of 1473.