diff --git a/src/nibbleslice.rs b/src/nibbleslice.rs
index 5866ed8f0..6ccf695c0 100644
--- a/src/nibbleslice.rs
+++ b/src/nibbleslice.rs
@@ -38,6 +38,11 @@ impl<'a> NibbleSlice<'a> {
 	/// Create a new nibble slice with the given byte-slice with a nibble offset.
 	pub fn new_offset(data: &'a [u8], offset: usize) -> NibbleSlice { NibbleSlice{data: data, offset: offset} }
 
+	/// Create a new nibble slice from the given HPE encoded data (e.g. output of `encoded()`).
+	pub fn from_encoded(data: &'a [u8]) -> (NibbleSlice, bool) {
+		(Self::new_offset(data, if data[0] & 16 == 16 {1} else {2}), data[0] & 32 == 32)
+	}
+
 	/// Is this an empty slice?
 	pub fn is_empty(&self) -> bool { self.len() == 0 }
 
@@ -148,6 +153,15 @@ mod tests {
 		assert_eq!(n.mid(1).encoded(true), &[0x31, 0x23, 0x45]);
 	}
 
+	#[test]
+	fn from_encoded() {
+		let n = NibbleSlice::new(D);
+		assert_eq!((n, false), NibbleSlice::from_encoded(&[0x00, 0x01, 0x23, 0x45]));
+		assert_eq!((n, true), NibbleSlice::from_encoded(&[0x20, 0x01, 0x23, 0x45]));
+		assert_eq!((n.mid(1), false), NibbleSlice::from_encoded(&[0x11, 0x23, 0x45]));
+		assert_eq!((n.mid(1), true), NibbleSlice::from_encoded(&[0x31, 0x23, 0x45]));
+	}
+
 	#[test]
 	fn shared() {
 		let n = NibbleSlice::new(D);
diff --git a/src/rlp.rs b/src/rlp.rs
index 1703850bb..e8562828a 100644
--- a/src/rlp.rs
+++ b/src/rlp.rs
@@ -227,10 +227,6 @@ impl<'a> Rlp<'a> {
 		From::from(self.rlp.at(index).unwrap())
 	}
 
-	pub fn data_at(&self, _index: usize) -> &[u8] {
-		unimplemented!();
-	}
-
 	/// No value
 	/// 
 	/// ```rust
diff --git a/src/trie.rs b/src/trie.rs
index 26eaafb2b..4aebc688f 100644
--- a/src/trie.rs
+++ b/src/trie.rs
@@ -88,6 +88,19 @@ impl TrieDB {
 				unimplemented!();
 			},
 			Prototype::List(2) => {
+				let their_key_rlp = o.at(0);
+				let (them, _) = NibbleSlice::from_encoded(their_key_rlp.data());
+				match partial_key.common_prefix(&them) {
+					0 => {
+						// transmute to branch here
+					},
+					cp if cp == them.len() => {
+						// fast-forward
+					},
+					_ => {
+						// cleve into two + branch in the middle
+					},
+				}
 				// already have an extension. either fast_forward, cleve or transmute_to_branch.
 				unimplemented!();
 			},
@@ -143,7 +156,5 @@ fn playpen() {
 	assert!(t.is_empty());
 
 	t.insert(&[0x01u8, 0x23], &[0x01u8, 0x23]);
-	assert_eq!(*t.root(), trie_root(vec![
-									(vec![1u8, 0x23], vec![1u8, 0x23])
-	]));
+	assert_eq!(*t.root(), trie_root(vec![ (vec![1u8, 0x23], vec![1u8, 0x23]) ]));
 }