diff --git a/R/sampler-nested-adaptive.R b/R/sampler-nested-adaptive.R
index 7f919921..9f19417a 100644
--- a/R/sampler-nested-adaptive.R
+++ b/R/sampler-nested-adaptive.R
@@ -159,7 +159,8 @@ mcstate_sampler_nested_adaptive <- function(initial_vcv,
       list(base = autocorrelation_base, groups = autocorrelation_groups)
     internal$vcv <- list(base = vcv_base, groups = vcv_groups)
     proposal_vcv <- list(base = proposal_vcv_base, groups = proposal_vcv_groups)
-    internal$proposal <- nested_proposal(proposal_vcv, model$parameter_groups)
+    internal$proposal <- nested_proposal_adaptive(proposal_vcv,
+                                                  model$parameter_groups)
     
     internal$history_pars <- numeric()
     internal$included <- integer()
@@ -311,7 +312,8 @@ mcstate_sampler_nested_adaptive <- function(initial_vcv,
     
     ## Update proposal
     proposal_vcv <- list(base = proposal_vcv_base, groups = proposal_vcv_groups)
-    internal$proposal <- nested_proposal(proposal_vcv, model$parameter_groups)
+    internal$proposal <- nested_proposal_adaptive(proposal_vcv,
+                                                  model$parameter_groups)
     
     state
   }
@@ -425,3 +427,66 @@ check_nested_adaptive <- function(x, n_groups, has_base, null_allowed = FALSE,
   
   ret
 }
+
+
+## TODO: this is a simpler version of nested_proposal that does not
+## cope with boundaries etc - that's being looked at in #46 for now.
+## nocov start
+nested_proposal_adaptive <- function(vcv, parameter_groups, call = NULL) {
+  i_base <- parameter_groups == 0
+  n_base <- sum(i_base)
+  n_groups <- max(parameter_groups)
+  i_group <- lapply(seq_len(n_groups), function(i) which(parameter_groups == i))
+  if (NROW(vcv$base) != n_base) {
+    cli::cli_abort(
+      c("Incompatible number of base parameters in your model and sampler",
+        i = paste("Your model has {n_base} base parameters, but 'vcv$base'",
+                  "implies {NROW(vcv$base)} parameters")),
+      call = call)
+  }
+  if (length(vcv$groups) != n_groups) {
+    cli::cli_abort(
+      c("Incompatible number of parameter groups in your model and sampler",
+        i = paste("Your model has {n_groups} parameter groups, but",
+                  "'vcv$groups' has {length(vcv$groups)} groups")),
+      call = call)
+  }
+  n_pars_by_group <- lengths(i_group)
+  n_pars_by_group_vcv <- vnapply(vcv$groups, nrow)
+  err <- n_pars_by_group_vcv != n_pars_by_group
+  if (any(err)) {
+    detail <- sprintf(
+      "Group %d has %d parameters but 'vcv$groups[[%d]]' has %d",
+      which(err), n_pars_by_group[err],
+      which(err), n_pars_by_group_vcv[err])
+    cli::cli_abort(
+      c("Incompatible number of parameters within parameter group",
+        set_names(detail, "i")),
+      call = call)
+  }
+
+  has_base <- n_base > 0
+  if (has_base) {
+    mvn_base <- make_rmvnorm(vcv$base)
+    proposal_base <- function(x, rng) {
+      ## This approach is likely to be a bit fragile, so we'll
+      ## probably want some naming related verification here soon too.
+      x[i_base] <- mvn_base(x[i_base], rng)
+      x
+    }
+  } else {
+    proposal_base <- NULL
+  }
+
+  mvn_groups <- lapply(vcv$groups, make_rmvnorm)
+  proposal_groups <- function(x, rng) {
+    for (i in seq_len(n_groups)) {
+      x[i_group[[i]]] <- mvn_groups[[i]](x[i_group[[i]]], rng)
+    }
+    x
+  }
+
+  list(base = proposal_base,
+       groups = proposal_groups)
+}
+## nocov end