UPDATE 2-UK shares roar into 2020; midcaps hit fresh record

* FTSE 100 up 0.8%, FTSE 250 up 1%
* Investors welcome China policy easing
* U.S., China to sign Phase 1 deal on Jan. 15
* Tullow Oil sinks after Carapa drilling results

(Adds news items, analyst comments, updates to closing prices)
By Shashwat Awasthi
Jan 2 (Reuters) - Britain's stock market indexes surged in
the first trading session of the new decade, as investors
welcomed China's monetary policy easing and U.S. President
Donald Trump set the date for sealing a Phase 1 trade deal with
Beijing.
The FTSE 100 .FTSE jumped after two straight sessions of
losses to rise 0.8% after China cut the reserve requirement
ratio (RRR) for banks and Trump said a Phase 1 trade deal with
Beijing would be signed on Jan. 15. Mining shares .FTNMX1770 and oil majors were among the top
gainers, with Antofagasta ANTO.L , Glencore GLEN.L and BP
BP.L advancing between 2%-3.1%.
The FTSE 250 .FTMC soared 1% to notch up a fresh record
high and the British indexes enjoyed their best day since
mid-December, when Prime Minister Boris Johnson's election win
and de-escalating trade tensions had triggered a rally in
equities.
Gains were further supported by strong demand for cyclical
stocks such as banks, that led blue-chips Lloyds LLOY.L and
Barclays higher by 2% and 3%, respectively.
But despite Thursday's rise, which came after two sessions
of profit-taking following the FTSE 100's best run in three
years, analysts warned against getting carried away, citing thin
trading volume and calling China's policy predictable.
"The move on the RRR had been well telegraphed but came as a
welcome New Year's gift," OANDA analyst Jeffrey Halley said.
Cityindex analyst Ken Odeluga echoed that Beijing's policy
decision wasn't surprising, adding that though a signing date
for Phase 1 was set, uncertainties remained about if and when
more comprehensive trade agreements would be nailed down.
"As much as investors are keen to ring-in the New Year with
sure-footed gains, these influences are of course 'so 2019'," he
said.
"Predicating a positive risk-asset rally on them continues
to ignore a whole host of well-rehearsed reasons to remain
cautious."
Tullow Oil TLW.L , which plummeted more than 70% last month
after it scrapped its dividend and its CEO stepped down, plunged
as much as 20% following underwhelming results of drilling at
its Carapa-1 well offshore Guyana. "The results from the Carapa-1... are, in our view, a
negative," Berenberg analysts wrote. They added that the four
metres of net oil pay reported from the well was unlikely to be
commercial.