Some original ideas in quite a tough puzzle – held up by the 22-letter entry along the top and the 13-letter one in the first column.
Solving time: 30 mins
* = anagram
ACROSS
1/2 A STITCH IN TIME SAVES NINE (investment is a tie; cash in)* A very long anagram, I saw the phrase when I had a few letters from crossing answers.
10 A D(V)ENTURE A commercial speculation
11 MINCE Subtle, this. this = mince indicating an anagram of (nice and m = bit of meat). Some argue ‘bit’ is too vague to indicate the first letter as it could be any bit of the word. I thought that Nice might hint at a French reference. This was my last answer.
14 TR (IFF) ID All reversed. From John Wyndham’s SF novel The Day of the Triffids which I read a long time ago so this was my first answer to go in.
16 DEE P SEA
18 PRESAG E (grapes)* Saw the wordplay straightaway, but took a while to see the answer.
20 PA’S TIES A little uneasy about tie = accessory if I’ve got this right.
21 L (I BERT) INE
23 Tony B LAIR
26 LADY-IN-WAITING Saw this possibility straightaway from the enumeration, but was unsure about it. Think what’s intended in one works in a palace (attending a royal household) or in the Ritz, as, say, a waitress, but not so sure about that.
DOWN
4 C (Tory = Conservative) RUSH (career vb) ED (Balls, Labour politician). Very tricky.
5 I C ELAND
6 TEMPTRESS Don’t quite see this – tress would be a hairpiece perhaps but not sure about the temp. Pretty confident about the answer though.
8 LAMBETH PALACE (a tall beech Pam)* This was excellent as Rowan could refer to many people or things. Official London home of the Archbishop of Canterbury, Rowan Williams, head of the Anglican Church.
15 F (RAG R) ANCY Nicely misleading as ‘elaborate’ could be an anagram indicator, but not here.
20 PLECTRA P for E in Electra
22 BALS A Bal = dance in French
23 B (L) EST
6D – I wondered about this too but a hairpiece would be a temporary tress, perhaps?
Didn’t like 26A but apart from that I thought this was a really good puzzle – perfectly pitched for a Monday.